Top level domains

4umi web

The system of addressing worldwide connected electronic resources by domain name has a long and interesting past. Connecting what and how has been subject of study since the first networks were built in the 40's and 50's of the twentieth century. The Internet Domain Name System (DNS) was deployed in January 1985. Also see RFC 921.

Historical reasons

The DNS scheme is a distributed database for information about resources on the Internet, replacing the prior "hosts.txt" system. The DNS contains resource records mapping domain names to the unique numeric IP addresses assigned to every computer on the Internet. The names are relatively easy to remember for humans, and certainly more pleasant to read than the digits and dots of IP address codes.

Domain names contain dots too, to mark different levels of detail in the address, not unlike the dots, hyphens and what-have-you in postal addresses and telephone numbers. The bit behind the last dot is the Top Level Domain or TLD. The different TLD's can be divided in activity- and locality-orientated names. The original concept was devised with the idea of seven addresses at the top level, the root .arpa and six three-letter ‘generic’ names, supplemented with the two-letter country codes from ISO 3166-1.

How countries deal with their TLD is decided by the local government. The UK has gone to great lengths making .uk stand out as the ‘over the top’ domain behind the .com and .org mammoths. Some countries have made their TLD their top export product by opening up their market to foreigners, most notably the owners of .tv, the 11,000 people of Tuvalu. The list has needed revision because countries have fallen apart into new countries at several occasions.

Most of the generic names were already established in 1980. By intergovernmental initiative and agreement .int was added in 1988, and after much talk seven additional names were added in 2001 and 2002, four unsponsored and three sponsored. Especially the .pro domain name took some deliberation, but the system is now stable and solid.

Follows a list of the tld's or top level domains existing today, 1 May 2005.

Generic TLD's

Regional TLD's