Internet domain names are organized by their levels, with the higher levels on the right. For example, for the domain "mail.twenty.net" the top-level domain is "net", the second-level domain is "twenty.net", and the third-level domain is "www.twenty.net". Originally, the top-level Internet domains were associated with organizations, mainly ".arpa", ".csnet", ".bitnet", and ".uucp". On January 28, 1986, coincidentally the same day the Challenger space shuttle exploded, those same four organizations met at SRI and agreed to restructure the domain name space into the subject-specific top-level domains, with technical administration performed by ISI.
Top Level Domain Names
