And DNS on a TCP/IP network such as the Internet domain name and host name and IP address correspond to management system. Points to the system will be operated only within the Organization’s network, such as corporate domain name management system out there, but generally to manage domain names on the Internet. You can put an alias in a sequence of letters or characters in a numeric column is called the IP address in a TCP/IP network to identify individual computers and networks, but approachable man known as a host name or domain name. DNS is a distributed database of world-wide records and management information such as the domain name and host name and the corresponding IP address. Software and manage domain name information, respond to inquiries from foreign computer and software that asks a question to the DNS server, the DNS server and domain name from the corresponding IP addresses, and vice versa (this work called name resolution) to ask that the DNS client or DNS resolver (name resolver). Domain name has a hierarchical structure, each hierarchical domain administrative rights is transferring domain-owned organization. DNS servers are managed in a hierarchical structure according to this, the parent domain’s DNS server doesn’t have control over all information on the domains, not know only to manage domains DNS server address (IP address). Placed in several places all over the world to manage top-level Internet domain (root domain) DNS server (root server) and know the location of the server that manages each top-level domain (for example,.jp and com). Each top-level domain DNS server and understand (co.jp, google.com, etc) the second-level domains under DNS server address, contact each DNS server in turn from the top you can get in that lowest level of individual domain name information.