Top-level domains (TLDs)

As of 2003, there were two-letter top-level domains, TLDs, for each country and a special top-level domain .ARPA which currently contains some Internet infrastructure databases.

In addition, there are additional top-level domains .AERO, .BIZ, .COM, .COOP, .EDU, .GOV, .INFO, .INT, .MIL, .MUSEUM, .NAME, .NET, .ORG, and .PRO (this list is probably going to be expanded regularly and should not be relied on as comprehensive).

Each country-specific top-level domain has its own registration policies. Many only accept registration from entities or individuals that can demonstrate strong ties to that country.

.EDU, .INT, .MIL and .GOV have restrictive conditions on who can register names in those domains (respectively, four-year degree granting institutions in North America, organisations that were established by international treaty, the USA military, and the USA federal government).

Most of the other top-level domains are operated on commercial principles.

• Domain name registries around the world is a highly comprehensive list of TLD registries maintained by the .NO domain registry.
• The two-letter country code top level domains (ccTLDs) are based on the ISO 3166-1 English two-letter country codes. There are some discrepancies: for instance .UK is the ccTLD for the United Kingdom, even though the ISO 3166 code for this country is GB. The ccTLD database from IANA contains information about all the ccTLDs that have been delegated.
• root hints file, also known as named.ca, listing current root servers (last updated 29-Jan-2004: checked 19-Mar-2004).

Top-level domain controversy

Controversy raged for several years about IANA having sole control of top level domains, and about NSI having control over the commercially focused top level domains .COM, .NET, and .ORG. One proposal to regulate other registries at the top level was originally formalised as the gTLD-MoU. In the end, ICANN obtained control of the top level domains, replacing IANA with a body that is somewhat more open to outside input (if you are a government or represent large business). However, ICANN still has a long way to go before it is accepted by the general Internet community, especially since it is proposing to consolidate several contentious functions in one body. Control of the root servers is currently distributed between several volunteer organisations, and some critics have expressed concern over ICANN's proposed direct management of these critical infrastructure elements. Evoking criticism from a different front, ICANN is also seeking increasing control over IP address allocations.

One of several dissenting views was that of the AlterNIC. Read about the type of tactics the AlterNIC employed to make its case. On the other hand, ICANN also has a lot to answer for; here is an example critique from roving_reporter.

The debate leading to the formation of ICANN is reasonably well covered by Wired. The original source is the White House Green Paper.

Current debates about TLDs and DNS oversight are covered well by CircleID.

Root servers

See www.root-servers.org for information on the root servers. Most of the individual root servers consist of multiple machines which share a single IP address using various routing mechanisms. For instance, in early 2004, K.ROOT-SERVERS.NET was actually located in three separate locations in Europe.