Domain Name System (DNS) domain setup requires domain name registration to prevent others from using your domain name.
DNS allows you to serve names and addresses on an intranet, or internal network. It also allows you to serve names and addresses to the rest of the world through the Internet. If you want to set up domains on the Internet, you are required to register a domain name.
If you are setting up an intranet, you are not required to register a domain name for internal use. Whether to register an intranet name depends on whether you want to ensure that no one else can ever use the name on the Internet, independent of your internal use. Registering a name that you are going to use internally ensures that you will never have a conflict if you later want to use the domain name externally.
Domain registration can be performed by direct contact with an authorized domain name registrar, or through some Internet Service Providers (ISPs). Some ISPs offer a service to submit domain name registration requests on your behalf. The Internet Network Information Center (InterNIC) maintains a directory of all domain name registrars that are authorized by the Internet Corporation for Assigned Names and Numbers (ICANN).