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The Top Level Domain (TLD) is always the last part of a domain name, such as .com, .net, .us, etc.[1] Each TLD is managed by a single Registry.


The need for a hierarchical DNS arose with the popularity of the Internet in academic spheres in the early 1980s, which eventually necessitated a de-centralized Internet. Communications between The Stanford Research Institute NIC and other institutions included plans to create a hierarchical DNS, found in RFC 805, a group document from 1982. This document outlines many of the basics of the eventual DNS, including the need for TLDs to provide a fixed starting point for queries, and the need for SLDs to be unique. This, in turn, would necessitate the need for a registrar type of administration, and help the nascent IT community recognize that the distribution of responsibility for each domain to individual name servers would provide administrative advantages.[2]

Varieties of TLDs

There are different types of TLDs.

These TLDs operate in different manners, and can be categorized in some simple ways:

  • Operating Mode
    • Open - Operating and offering both registration and resolution services.
    • Closed - Not accepting registrations, may be resolving evergreen/legacy/infrastructure subdomains.
  • Level of Restriction
    • Unrestricted - If there are no requirements that must be met in order to register a name under a TLD, that TLD is Unrestricted.
    • Restricted - Requiring Local Physical Address, Local Tax ID, or other specific criteria be met to qualify in order to provision a name.
    • Sponsored - A variation on Restricted, the applicant for a domain in an STLD must meet the requirements within that TLD (ie. .jobs would require that Human Resources be involved, .travel would require certain Travel criteria are met, etc).


At its Seoul conference in 2009, ICANN approved the IDN ccTLD fast track process, which made way for ccTLDs to be written in non-latin characters. Russia, Egypt, Saudi Arabia, and United Arab Emirates are some of the first countries to advance in the application and implementation process.[3]


  1. TLD
  2. Living Internet

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