Top-Level Domain
Acronym: Top Level Domain
The 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.
History
The need for a hierarchical DNS arose with the popularity of the Internet in academic spheres in the early 1980s. This eventually necessitated a de-centralized Internet. Communications between The Stanford Research Institute NIC and other institutions include 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).