RDAP Bootstrapping

“Bootstrapping” is, according to WikiPedia:

In general, bootstrapping usually refers to a self-starting process that is supposed to continue or grow without external input.

In RDAP, it is the first process to finding an RDAP server, and the last when the RDAP server being sought is that for either a TLD (ccTLD or gTLD) or the IANA. This process is defined by RFC 9224, which a client may execute explicitly or via a redirect server as described in RFC 7480.

There is no official list of RDAP bootstrap services, however two of the most popular are the ones run by ARIN and RDAP.ORG, the latter of which reports 10 million query redirects daily.

The title of RFC 9224, “Finding the Authoritative Registration Data Access Protocol (RDAP) Service” is misleading in that the RFC only describes the discovery of RDAP sources registered with IANA. Important as those sources may be, they are not “authoritative” for second and third level domain registries (e.g. co.uk), IP addresses and Autonomous System Numbers transferred between RIRs, number resources of NIRs and LIRs, and domain contacts of “thin” TLDs where the information resides solely at a domain registrar.

The Bootstrap Files

Bootstrapping starts with one of 5 IANA files, depending on the information being sought.

For all but Object Tags, the files are structured as illustrated in RFC 9224:

{
  "version": "1.0",
  "publication": "YYYY-MM-DDTHH:MM:SSZ",
  "description": "Some text",
  "services": [
    [
      ["entry1", "entry2", "entry3"],
      [
        "https://registry.example.com/myrdap/",
        "http://registry.example.com/myrdap/"
      ]
    ],
    [
      ["entry4"],
      [
        "https://example.org/"
      ]
    ]
  ]
}

The entries are either domain names (e.g. “.com”, “.xyz”), IP address CIDR blocks (either v6 or v4), or Autonomous System Number (ASN) ranges, and the arrays are the RDAP Base URLs of the services for those resources.

Each entry type as a specific matching strategy:

The IANA is the Root

IANA is represented as an empty string (“”) in the dns.json file. Though IANA’s base URLs are only represented in the dns.json file, this should not be misconstrued to mean IANA’s RDAP services only contain TLD information.

As of this writing, IANA has not placed their RDAP URLs into the RDAP dns.json bootstrap file as root (“”), though there is an entry for “.int”.

Object Tags

Object Tags were introduced as a mechanism to provide bootstrapping to things in RDAP that had no natural bootstrapping process, mostly RDAP entities. That is, RFC 8521 defines how tags can be applied to objects which can also be used to find the servers where those objects are defined.

In more simple terms, this means identifying a suffix on a string is an object tag and then querying the server for it. For example, an entity with a handle of “FOO-ARIN” can be found in the ARIN RDAP server because the handle name is suffixed by “-ARIN”.

Object tags can also be used to direct clients at RDAP services using “short names”. Neither usage is in widespread use.