NET -- network Web sites, though open to everyone
ORG -- non-profit organization Web sites, though open to everyone
EDU -- restricted to schools and educational organizations
MIL -- restricted to the U.S. military
GOV -- restricted to the U.S. government
US, UK, RU and other two-letter country codes -- each is assigned to a domain name authority in the respective country
2. If it doesn't have the domain name and IP address in its database, it contacts another DNS server on the Internet. It may have to do this multiple times.
3. If it has to contact another DNS server, it caches the lookup results for a limited time so it can quickly resolve subsequent requests to the same domain name.
4. If it has no luck finding the domain name after a reasonable search, it returns an error indicating that the name is invalid or doesn't exist.