There are public DNS name spaces and private DNS name spaces.
Public DNS Namespace
The DNS namespace in the Internet DNS infrastructure is the public DNS namespace. The Root of the Internet public DNS namespace and the Top Level Domains (TLDs) are managed by the Internet Corporation for Assigned Names and Numbers (ICANN). Internet Corporation for Assigned Names and Numbers (ICANN) maintains Root Level and TLD Level DNS Servers.
Internet Corporation for Assigned Names and Numbers (ICANN) allocates Domains names (Example: omnisecu.com, cisco.com, microsoft.com) under the Top Level Domains for public via agencies called as "Domain Name Registrars".
fastdomain.com, godaddy.com, hostgator.com are examples of ICANN authorized domain name registrars.
There are three types of TLDs (Top Level Domains).
1) Organizational Top Level Domains: Organizational Top Level Domains are primarily used to indicate the nature of the organization.
Some of the Organizational Top Level Domains are listed below.
|Public Top Level Domain
||U.S. government organizations
||Organizations established by international treaties
||Network Service providers
||travel and tourism industry
2) Geographical Top Level Domains: Geographical domains are named using the Two Character country identifier. Geographical domains are usually allocated to organizations belong to a particular Geographical area.
Example: .in. for India, .au. for Australia, .sa. for Saudi Arabia, .il., for Israel etc.
3) Reverse Domains: Reverse Domains are used to reverse lookup (IP Address to Name resolution)
Private DNS name spaces
A private namespace is normally defined inside DNS infrastructure of a private organization, which is not used in the public internet. Within a Private Namespace, an organization can maintain their own DNS namespace and DNS Root.A private namespace is not published in the Internet. Name resolution of resources belongs to private namespaces are not possible from public DNS infrastructure. Private namespace are not directly accessible from the public Internet.
Example omnisecu.internal., omnisecu.private., omnisecu.local.