Domain Name System (DNS). Domain Name System (DNS) is a database system that work transla
tes a fully qualified domain name of the computer to the Internet Protocol or IP address. Computer network using IP addresses to locate and connect one computer to another computer, but IP addresses can be difficult for people to remember. Here DNS allows you to connect to a computer network using the user-friendly domain names rather than numerical IP addresses. Conversely, Reverse DNS (rDNS) will translate IP addresses into domain names.
Any organization or a collection that has a computer network will have at least one server handling DNS requests. where the server, called server name, will hold a list of all IP addresses in the network, plus the IP address cache for Domain Name System (DNS) recently accessed computers outside the network. Each computer on each network needs to know the location of only one name server. When a computer requests an IP address, one of three things happens, depending on whether the requested IP address in your local network:
Domain Name System (DNS)
If the requested IP address is registered locally (for example, that in your organization’s network), you will receive an immediate response from one of the local name server listed in the configuration of your workstation. In this case, there is usually little or no wait for a response.
If the requested IP address is not registered locally (ie, outside of your organization’s network), but someone in your organization recently asked the same IP address, then the local name server will retrieve the IP address of the cache. Once again, there should be little or no wait for a response.
If the requested IP address is not registered locally, and you are the first to ask for information about this system in a certain period of Domain Name System (DNS
) time (ranging from 12 hours to one week), then the local name server will perform a search in the name of your workstation.
This search may involve two or more query other name servers at potentially very remote locations. This question c
an take anywhere from one to two seconds to one minute is usually dependent on h ow well you connect to a remote network and how many intermediate name servers must be contacted. Sometimes, because the protocol used to control light, you may not receive a response. In this case, your workstation or client software may c ontinue to repeat the request until a response is received, or you may receive an error message.
Domain Name System (DNS)
When you use an application such as te
lnet to connect to another computer, you most likely type in the domain name instead of IP address of that computer. Telnet application takes the domain name an d use one of the above methods to retrieve the corresponding IP address of the server name.
A good analogy is to think of DNS as an electronic phone book for a computer network. If you know the name of the computer, the server name to find
its IP address.