Domain name can be easily understood as a registered address of a commercial unit or organization on the Internet. It is reflected by an IP address of server on the interntional internet network. Different servers on the internet are recognized by IP address. However, IP address is dull figures and hard to remember, thus a easily remembered name -- domain name is created to reflect the IP address. Therefore, domain name is exclusive all over the world. Besides the most commonly utilized international domain name -- top level domain name, there is also second level domain name which is followed by country code. The top-level domain name is administrated by InterNIC.