The HOSTS system is fine for resolving host names within a network, but with millions of hosts worldwide, it's obviously impractical for resolving the names of computers the reside outside your subnet.

      You might think that because the InterNIC handles all registration duties for domains, your TCP/IP applications could just query some kind of central database at the InterNIC to resolve host names. There are two problems with this approach: The number queries this database would have to handle would be astronomical ( and thus extremely slow), and you'd have to contact the InterNIC every time you added a host to your network (as ISP's). Because it now takes a few weeks to get a domain registered, it's reasonable to assume that it would take at least as long to get your host onto the database, which is unacceptable.

      Instead of one central database of host names and IP addresses, the internet uses a distributed database system called Domain Name System (DNS). The DNS database uses a hierarchical structure to organize domains. The top level of this hierarchy consists of seven categories, as described below.

      The most famous geographic domains that related to countries.

Addition of new domains

     The International Ad Hoc committee (IAHC) declared a plan to add some new domains to the DNS.This was declared in 1997.