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Registration Data Access Protocol gTLD Profile

The Registration Data Access Protocol (RDAP) gTLD Profile maps policy and contractual requirements for gTLD registries and registrars to technical features in the Registration Data Access Protocol. This new protocol was created as a replacement for the WHOIS protocol. Its advantages over the older protocol include:

  • Standardized query, response and error messages.
  • Secure access to data (i.e., over HTTPS).
  • Extensibility (e.g., makes it easy to add output elements).
  • A bootstrapping mechanism that makes it easy to find the authoritative server for a given query.
  • Standardized redirection/reference mechanism (e.g., from a thin registry to a registrar).
  • Builds on top of the well-known web protocol HTTP.
  • Internationalization support for registration data.
  • Provides the option to enable differentiated access (e.g., limited access for anonymous users and full access for authenticated users).

Profile Documentation


  • 1982 – The Internet Engineering Task Force (IETF) issued a protocol for a directory service for ARPANET users. This protocol has been in use ever since; it is referred to as WHOIS.
  • 2010 – The ICANN community holds discussions about the need for technical evolution of the WHOIS Service.
  • 2011
    • On 19 September, the Security and Stability Advisory Committee issues SAC 051, which advises the ICANN community to evaluate and adopt a replacement for the existing domain name registration data access protocol (WHOIS).
    • On 28 October, the ICANN Board adopts SAC 051.
  • 2012
  • 2015
    • In March, the WEIRDS working group finalizes RFCs defining the Registration Data Access Protocol.
    • In September, ICANN begins consulting the Internet community on a draft version of the RDAP gTLD Profile. These discussions take place over the next 10 months, including a formal public comment period.
  • 2016 – On 26 July, ICANN published version 1.0 of the profile.
Domain Name System
Internationalized Domain Name ,IDN,"IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet ""a-z"". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European ""0-9"". The basic Latin alphabet together with the European-Arabic digits are, for the purpose of domain names, termed ""ASCII characters"" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of ""Unicode characters"" that provides the basis for IDNs. The ""hostname rule"" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen ""-"". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS. The following terminology is used when distinguishing between these forms: A domain name consists of a series of ""labels"" (separated by ""dots""). The ASCII form of an IDN label is termed an ""A-label"". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a ""U-label"". The difference may be illustrated with the Hindi word for ""test"" — परीका — appearing here as a U-label would (in the Devanagari script). A special form of ""ASCII compatible encoding"" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn--11b5bs1di. A domain name that only includes ASCII letters, digits, and hyphens is termed an ""LDH label"". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as"""" is not an IDN."