This document specifies a method to find which Registration Data Access Protocol (RDAP) server is authoritative to answer queries for a requested scope, such as domain names, IP addresses, or Autonomous System numbers. This document obsoletes RFC 7484.

This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9224.

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Querying and retrieving registration data from registries are defined in the Registration Data Access Protocol (RDAP) [RFC 7480] [RFC 7481] [RFC 9082] [RFC 9083]. These documents do not specify where to send the queries. This document specifies a method to find which server is authoritative to answer queries for the requested scope. Top-Level Domains (TLDs), Autonomous System (AS) numbers, and network blocks are delegated by IANA to Internet registries such as TLD registries and Regional Internet Registries (RIRs) that then issue further delegations and maintain information about them. Thus, the bootstrap information needed by RDAP clients is best generated from data and processes already maintained by IANA; the relevant registries already exist at [ipv4reg], [ipv6reg], [asreg], and [domainreg]. This document obsoletes [RFC 7484]. Per this document, IANA has created new registries based on a JSON format specified in this document, herein named RDAP Bootstrap Service Registries. These new registries are based on the existing entries of the above-mentioned registries. An RDAP client fetches the RDAP Bootstrap Service Registries, extracts the data, and then performs a match with the query data to find the authoritative registration data server and appropriate query base URL.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC 2119] [RFC 8174] when, and only when, they appear in all capitals, as shown here.

The RDAP Bootstrap Service Registries, as specified in Section 12 below, have been made available as JSON [RFC 8259] objects, which can be retrieved via HTTP from locations specified by IANA. The JSON object for each registry contains a series of members containing metadata about the registry such as a version identifier, a timestamp of the publication date of the registry, and a description. Additionally, a "services" member contains the registry items themselves, as an array. Each item of the array contains a second-level array, with two elements, each of them being a third-level array. Each element of the Services Array is a second-level array with two elements: in order, an Entry Array and a Service URL Array. The Entry Array contains all entries that have the same set of base RDAP URLs. The Service URL Array contains the list of base RDAP URLs usable for the entries found in the Entry Array. Elements within these two arrays are not ordered in any way. An example structure of the JSON output of an RDAP Bootstrap Service Registry is illustrated: The formal syntax is described in Section 10. The "version" corresponds to the format version of the registry. This specification defines version "1.0". The syntax of the "publication" value conforms to the Internet date/time format [RFC 3339]. The value is the latest update date of the registry by IANA. The optional "description" string can contain a comment regarding the content of the bootstrap object. Per [RFC 7258], in each array of base RDAP URLs, the secure versions of the transport protocol SHOULD be preferred and tried first. For example, if the base RDAP URLs array contains both HTTPS and HTTP URLs, the bootstrap client SHOULD try the HTTPS version first. Base RDAP URLs MUST have a trailing "/" character because they are concatenated to the various segments defined in [RFC 9082]. JSON names MUST follow the format recommendations of Section 6 of RFC 7480. Any unrecognized JSON object properties or values MUST be ignored by implementations. Internationalized Domain Name labels used as entries or base RDAP URLs in the registries defined in this document MUST be only represented using their A-label form as defined in [RFC 5890]. All Domain Name labels used as entries or base RDAP URLs in the registries defined in this document MUST be only represented in lowercase.

The JSON output of this registry contains domain label entries attached to the root, grouped by base RDAP URLs, as shown in this example. The domain name's authoritative registration data service is found by doing the label-wise longest match of the target domain name with the domain values in the Entry Arrays in the IANA "Bootstrap Service Registry for Domain Name Space". The match is done per label, from right to left. If the longest match results in multiple entries, then those entries are considered equivalent. The values contained in the Service URL Array of the matching second-level array are the valid base RDAP URLs as described in [RFC 9082]. For example, a domain RDAP query for a.b.example.com matches the com entry in one of the arrays of the registry. The base RDAP URL for this query is then taken from the second element of the array, which is an array of base RDAP URLs valid for this entry. The client chooses one of the base URLs from this array; in this example, it chooses the only one available, "https://registry.example.com/myrdap/". The segment specified in [RFC 9082] is then appended to the base URL to complete the query. The complete query is then "https://registry.example.com/myrdap/domain/a.b.example.com". If a domain RDAP query for a.b.example.com matches both com and example.com entries in the registry, then the longest match applies and the example.com entry is used by the client. If the registry contains entries such as com and goodexample.com, then a domain RDAP query for example.com only matches the com entry because matching is done on a per-label basis. The entry for the root of the domain name space is specified as "".

This section discusses IPv4 and IPv6 address space and Autonomous System numbers. For IP address space, the authoritative registration data service is found by doing a longest match of the target address with the values of the arrays in the corresponding RDAP Bootstrap Service Registry for Address Space. The longest match is done the same way as in packet forwarding: the addresses are converted in binary form and then the binary strings are compared to find the longest match up to the specified prefix length. The values contained in the second element of the array are the base RDAP URLs as described in [RFC 9082]. The longest match method enables covering prefixes of a larger address space pointing to one base RDAP URL while more specific prefixes within the covering prefix are being served by another base RDAP URL.

The JSON output of this registry contains IPv4 prefix entries, specified in Classless Inter-domain Routing (CIDR) format [RFC 4632] and grouped by RDAP URLs, as shown in this example. For example, a query for "192.0.2.1/25" matches the "192.0.0.0/8" entry and the "192.0.2.0/24" entry in the example registry above. The latter is chosen by the client because it is the longest match. The base RDAP URL for this query is then taken from the second element of the array, which is an array of base RDAP URLs valid for this entry. The client chooses one of the base URLs from this array; in this example, it chooses the only one available, "https://example.org/". The {resource} specified in [RFC 9082] is then appended to the base URL to complete the query. The complete query is then "https://example.org/ip/192.0.2.1/25".

The JSON output of this registry contains IPv6 prefix entries, using [RFC 5952] text representation of the address prefixes format, grouped by base RDAP URLs, as shown in this example. For example, a query for "2001:db8:1000::/48" matches the "2001:db8::/34" entry and the "2001:db8:1000::/36" entry in the example registry above. The latter is chosen by the client because it is the longest match. The base RDAP URL for this query is then taken from the second element of the array, which is an array of base RDAP URLs valid for this entry. The client chooses one of the base URLs from this array; in this example, it chooses "https://example.net/rdaprir2/" because it's the secure version of the protocol. The segment specified in [RFC 9082] is then appended to the base URL to complete the query. The complete query is therefore "https://example.net/rdaprir2/ip/2001:db8:1000::/48". If the target RDAP server does not answer, the client can then use another URL prefix from the array.

The JSON output of this registry contains entries for AS number ranges, grouped by base RDAP URLs, as shown in this example. The Entry Array is an array containing the list of AS number ranges served by the base RDAP URLs found in the second element. Each element of the array contains two AS numbers represented in decimal format, separated by a hyphen, that represents the range of AS numbers between the two AS numbers (inclusive), where values are in increasing order (e.g., 100-200, not 200-100). A single AS number is represented as a range of two identical AS numbers. AS numbers are represented as 'asplain' as defined in [RFC 5396]. Ranges MUST NOT overlap. For example, a query for AS 65411 matches the 64512-65534 entry in the example registry above. The base RDAP URL for this query is then taken from the second element of the array, which is an array of base RDAP URLs valid for this entry. The client chooses one of the base URLs from this array; in this example, it chooses "https://example.net/rdaprir2/". The segment specified in [RFC 9082] is then appended to the base URL to complete the query. The complete query is, therefore, "https://example.net/rdaprir2/autnum/65411". If the server does not answer, the client can then use another URL prefix from the array.

Entities (such as contacts, registrants, or registrars) can be queried by handle as described in [RFC 9082]. Since there is no global name space for entities, this document does not describe how to find the authoritative RDAP server for entities. However, it is possible that, if the entity identifier was received from a previous query, the same RDAP server could be queried for that entity, or the entity identifier itself is a fully qualified URL that can be queried. The mechanism described in [RFC 8521] MAY also be used.

The registries may not contain the requested value. In these cases, there is no known RDAP server for that requested value, and the client SHOULD provide an appropriate error message to the user.

This method relies on the fact that RDAP clients are fetching the IANA registries to then find the servers locally. Clients SHOULD NOT fetch the registry on every RDAP request. Clients SHOULD cache the registry, but use underlying protocol signaling, such as the HTTP Expires header field [RFC 7234], to identify when it is time to refresh the cached registry. Some authorities of registration data may work together on sharing their information for a common service, including mutual redirection [REDIRECT-RDAP]. When a new object is allocated, such as a new AS range, a new TLD, or a new IP address range, there is no guarantee that this new object will have an entry in the corresponding bootstrap RDAP registry, since the setup of the RDAP server for this new entry may become live and registered later. Therefore, the clients should expect that even if an object, such as TLD, IP address range, or AS range is allocated, the existence of the entry in the corresponding bootstrap registry is not guaranteed.

This method does not provide a direct way to find authoritative RDAP servers for any other objects than the ones described in this document. In particular, the following objects are not bootstrapped with the method described in this document:

• entities
• queries using search patterns that do not contain a terminating string that matches some entries in the registries
• nameservers
• help

This section is the formal definition of the registries. The structure of JSON objects and arrays using a set of primitive elements is defined in [RFC 8259]. Those elements are used to describe the JSON structure of the registries.

OBJECT:

a JSON object, defined in Section 4 of RFC 8259

MEMBER:

a member of a JSON object, defined in Section 4 of RFC 8259

MEMBER-NAME:

the name of a MEMBER, defined as a "string" in Section 4 of RFC 8259

MEMBER-VALUE:

the value of a MEMBER, defined as a "value" in Section 4 of RFC 8259

ARRAY:

an array, defined in Section 5 of RFC 8259

ARRAY-VALUE:

an element of an ARRAY, defined in Section 5 of RFC 8259

STRING:

a "string", as defined in Section 7 of RFC 8259

Using the above terms for the JSON structures, the syntax of a registry is defined as follows:

rdap-bootstrap-registry:

an OBJECT containing a MEMBER version and a MEMBER publication, an optional MEMBER description, and a MEMBER services-list

version:

a MEMBER with MEMBER-NAME "version" and MEMBER-VALUE a STRING

publication:

a MEMBER with MEMBER-NAME "publication" and MEMBER-VALUE a STRING

description:

a MEMBER with MEMBER-NAME "description" and MEMBER-VALUE a STRING

services-list:

a MEMBER with MEMBER-NAME "services" and MEMBER-VALUE a services-array

services-array:

an ARRAY, where each ARRAY-VALUE is a service

service:

an ARRAY of 2 elements, where the first ARRAY-VALUE is an entry-list and the second ARRAY-VALUE is a service-uri-list

entry-list:

an ARRAY, where each ARRAY-VALUE is an entry

entry:

a STRING

service-uri-list:

an ARRAY, where each ARRAY-VALUE is a service-uri

service-uri:

a STRING

By providing a bootstrap method to find RDAP servers, this document helps to ensure that the end users will get the RDAP data from an authoritative source instead of from rogue sources. The method has the same security properties as the RDAP protocols themselves. The transport used to access the registries uses TLS [RFC 8446]. Additional considerations on using RDAP are described in [RFC 7481].

IANA has created the RDAP Bootstrap Services Registries listed below and made them available as JSON objects. The contents of these registries are described in Sections [3], [4], and [5], with the formal syntax specified in Section 10. The registries MUST be accessible only through HTTPS (TLS [RFC 8446]) transport. The process for adding or updating entries in these registries differs from the normal IANA registry processes: these registries are generated from the data, processes, and policies maintained by IANA in their allocation registries ([ipv4reg], [ipv6reg], [asreg], and [domainreg]), with the addition of new RDAP server information. IANA updates RDAP Bootstrap Services Registries entries from the allocation registries as those registries are updated. This document does not change any policies related to the allocation registries; IANA has provided a mechanism for collecting the RDAP server information. IANA has created a new top-level category on the Protocol Registries page: <https://www.iana.org/protocols>. The group is called "Registration Data Access Protocol (RDAP)". Each of the RDAP Bootstrap Services Registries has been made available for on-demand download in the JSON format by the general public, and that registry's URI is listed directly on the Protocol Registries page. Other normal registries will be added to this group by other documents, but the reason the URIs for these registries are clearly listed on the main page is to make those URIs obvious to implementers -- these are registries that will be accessed by software, as well as by humans using them for reference information. Because these registries will be accessed by software, the download demand for the RDAP Bootstrap Services Registries may be unusually high compared to normal IANA registries. The technical infrastructure by which registries are published has been put in place by IANA to support the load. Since the publication of [RFC 7484], no issues have been reported regarding the load or the service. As discussed in Section 8, software that accesses these registries will depend on the HTTP Expires header field to limit their query rate. It is, therefore, important for that header field to be properly set to provide timely information as the registries change, while maintaining a reasonable load on the IANA servers. The HTTP Content-Type returned to clients accessing these JSON-formatted registries MUST be "application/json", as defined in [RFC 8259]. Because of how information in the RDAP Bootstrap Services Registries is grouped and formatted, the registry entries may not be sortable. It is, therefore, not required or expected that the entries be ordered in any way.

Entries in this registry contain at least the following:

• a CIDR [RFC 4632] specification of the network block being registered
• one or more URLs that provide the RDAP service regarding this registration

Entries in this registry contain at least the following:

• an IPv6 prefix [RFC 5952] specification of the network block being registered
• one or more URLs that provide the RDAP service regarding this registration

Entries in this registry contain at least the following:

• a range of Autonomous System numbers being registered
• one or more URLs that provide the RDAP service regarding this registration

Entries in this registry contain at least the following:

• a domain name attached to the root being registered
• one or more URLs that provide the RDAP service regarding this registration

[RFC2119]

S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC3339]

G. Klyne, and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.

[RFC4632]

V. Fuller, and T. Li, "Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 2006,
<https://www.rfc-editor.org/info/rfc4632>.

[RFC5396]

G. Huston, and G. Michaelson, "Textual Representation of Autonomous System (AS) Numbers", RFC 5396, DOI 10.17487/RFC5396, December 2008,
<https://www.rfc-editor.org/info/rfc5396>.

[RFC5890]

J. Klensin, "Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework", RFC 5890, DOI 10.17487/RFC5890, August 2010,
<https://www.rfc-editor.org/info/rfc5890>.

[RFC5952]

S. Kawamura, and M. Kawashima, "A Recommendation for IPv6 Address Text Representation", RFC 5952, DOI 10.17487/RFC5952, August 2010,
<https://www.rfc-editor.org/info/rfc5952>.

[RFC7258]

S. Farrell, and H. Tschofenig, "Pervasive Monitoring Is an Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May 2014,
<https://www.rfc-editor.org/info/rfc7258>.

[RFC7480]

A. Newton, B. Ellacott, and N. Kong, "HTTP Usage in the Registration Data Access Protocol (RDAP)", STD 95, RFC 7480, DOI 10.17487/RFC7480, March 2015,
<https://www.rfc-editor.org/info/rfc7480>.

[RFC8174]

B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.

[RFC8259]

T. Bray, "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.

[asreg]

IANA, "Autonomous System (AS) Numbers",
<https://www.iana.org/assignments/as-numbers>.

[domainreg]

IANA, "Root Zone Database",
<https://www.iana.org/domains/root/db>.

[ipv4reg]

IANA, "IANA IPv4 Address Space Registry",
<https://www.iana.org/assignments/ipv4-address-space>.

[ipv6reg]

IANA, "IPv6 Global Unicast Address Assignments",
<https://www.iana.org/assignments/ipv6-unicast-address-assignments>.

[REDIRECT-RDAP]

C.M. Martinez, L. Zhou, and G. Rada, "Redirection Service for Registration Data Access Protocol", Internet-Draft draft-ietf-weirds-redirects-04, July 2014,
<https://datatracker.ietf.org/doc/html/draft-ietf-weirds-redirects-04>.

[RFC7071]

N. Borenstein, and M. Kucherawy, "A Media Type for Reputation Interchange", RFC 7071, DOI 10.17487/RFC7071, November 2013,
<https://www.rfc-editor.org/info/rfc7071>.

[RFC7234]

R. Fielding, M. Nottingham, and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Caching", RFC 7234, DOI 10.17487/RFC7234, June 2014,
<https://www.rfc-editor.org/info/rfc7234>.

[RFC7481]

S. Hollenbeck, and N. Kong, "Security Services for the Registration Data Access Protocol (RDAP)", STD 95, RFC 7481, DOI 10.17487/RFC7481, March 2015,
<https://www.rfc-editor.org/info/rfc7481>.

[RFC7484]

M. Blanchet, "Finding the Authoritative Registration Data (RDAP) Service", RFC 7484, DOI 10.17487/RFC7484, March 2015,
<https://www.rfc-editor.org/info/rfc7484>.

[RFC8446]

E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.

[RFC8521]

S. Hollenbeck, and A. Newton, "Registration Data Access Protocol (RDAP) Object Tagging", BCP 221, RFC 8521, DOI 10.17487/RFC8521, November 2018,
<https://www.rfc-editor.org/info/rfc8521>.

[RFC9082]

S. Hollenbeck, and A. Newton, "Registration Data Access Protocol (RDAP) Query Format", STD 95, RFC 9082, DOI 10.17487/RFC9082, June 2021,
<https://www.rfc-editor.org/info/rfc9082>.

[RFC9083]

S. Hollenbeck, and A. Newton, "JSON Responses for the Registration Data Access Protocol (RDAP)", STD 95, RFC 9083, DOI 10.17487/RFC9083, June 2021,
<https://www.rfc-editor.org/info/rfc9083>.

There are no substantive changes except for minor clarifications. This update is primarily to meet the requirements for moving to an Internet Standard.

The WEIRDS Working Group had multiple discussions on this topic, including a session during IETF 84, where various methods such as in-DNS and others were debated. The idea of using IANA registries was discovered by the author during discussions with his colleagues as well as by a comment from Andy Newton. All the people involved in these discussions are herein acknowledged. Linlin Zhou, Jean-Philippe Dionne, John Levine, Kim Davies, Ernie Dainow, Scott Hollenbeck, Arturo Servin, Andy Newton, Murray Kucherawy, Tom Harrison, Naoki Kambe, Alexander Mayrhofer, Edward Lewis, Pete Resnick, Alessandro Vesely, Bert Greevenbosch, Barry Leiba, Jari Arkko, Kathleen Moriaty, Stephen Farrell, Richard Barnes, and Jean-Francois Tremblay provided input and suggestions to the first version of this document. Guillaume Leclanche was a coauthor of this document for some revisions; his support is therein acknowledged and greatly appreciated. The section on formal definition was inspired by Section 6.2 of RFC 7071. This new version [This document] received comments and suggestions from Gavin Brown, Patrick Mevzek, John Levine, Jasdip Singh, George Michaelson, Scott Hollenbeck, Russ Housley, Joel Halpern, Lars Eggert, Benjamin Kaduk, Scott Kelly, Éric Vyncke, John Scudder, Erik Kline, and Robert Wilton. Errata for RFC 7484 were submitted by Pieter Vandepitte and were applied to this document.

Marc Blanchet