Registration Data Access Protocol (RDAP) Query Format
American Registry for Internet Numbers
3635 Concorde Parkway
Chantilly
VA
United States
20151
andy@arin.net
http://www.arin.net
Verisign Labs
12061 Bluemont Way
Reston
VA
20190
United States
shollenbeck@verisign.com
http://www.verisignlabs.com/
This document describes uniform patterns to construct HTTP URLs that may be used to retrieve
registration information from registries (including both Regional Internet Registries (RIRs)
and Domain Name Registries (DNRs)) using "RESTful" web access patterns. These uniform patterns
define the query syntax for the Registration Data Access Protocol (RDAP).
This document describes a specification for querying registration data using a RESTful web
service and uniform query patterns. The service is implemented using the Hypertext Transfer
Protocol (HTTP) and the conventions described in
. These uniform patterns define the query syntax for
the Registration Data Access Protocol (RDAP).
The protocol described in this specification is intended to address deficiencies with the
WHOIS protocol that have been identified over time, including:
lack of standardized command structures;
lack of standardized output and error structures;
lack of support for internationalization and localization; and
lack of support for user identification, authentication, and access control.
The patterns described in this document purposefully do not encompass all of the methods employed
in the WHOIS and other RESTful web services used by the RIRs and DNRs. The intent of the patterns
described here are to enable queries of:
networks by IP address;
Autonomous System (AS) numbers by number;
reverse DNS metadata by domain;
nameservers by name;
registrars by name; and
entities (such as contacts) by identifier.
Server implementations are free to support only a subset of these features depending on local requirements.
Servers MUST return an HTTP 501 (Not Implemented) response to inform clients of
unsupported query types. It is also envisioned that each registry will continue to maintain WHOIS
and/or other RESTful web services specific to their needs and those of their constituencies, and the information
retrieved through the patterns described here may reference such services.
Likewise, future IETF standards may add additional patterns for additional query types. A simple pattern
namespacing scheme is described in to accommodate custom extensions that will not
interfere with the patterns defined in this document or patterns defined in future IETF standards.
WHOIS services, in general, are read-only services. Therefore, URL patterns
specified in this document are only applicable to the HTTP GET and HEAD methods.
This document does not describe the results or entities returned from issuing
the described URLs with an HTTP GET. The specification of these entities is described in
.
Additionally, resource management, provisioning, and update functions are out of
scope for this document. Registries have various and divergent methods covering these
functions, and it is unlikely a uniform approach is needed for interoperability.
HTTP contains mechanisms for servers to authenticate clients and for clients to authenticate servers (from which
authorization schemes may be built), so such mechanisms are not described in this document. Policy, provisioning,
and processing of authentication and authorization are out of scope for this document as deployments will have to
make choices based on local criteria. Supported authentication mechanisms are described in .
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" in this document are to be interpreted as described in .
IDN: Internationalized Domain Name
IDNA: Internationalized Domain Names in Applications, a protocol for the handling of IDNs.
DNR: Domain Name Registry
NFC: Unicode Normalization Form C
NFKC: Unicode Normalization Form KC
RDAP: Registration Data Access Protocol
REST: Representational State Transfer. The term was first described in a doctoral dissertation .
RESTful: An adjective that describes a service using HTTP and the principles of REST.
RIR: Regional Internet Registry
The base URLs used to construct RDAP queries are maintained in an IANA registry described in
. Queries are formed by retrieving an appropriate base URL from the
registry and appending a path segment specified in either Sections or .
Generally, a registry or other service provider will provide a base URL that identifies the protocol, host,
and port, and this will be used as a base URL that the complete URL is resolved against, as per Section 5
of RFC 3986 . For example, if the base URL is "https://example.com/rdap/", all RDAP query
URLs will begin with "https://example.com/rdap/".
The bootstrap registry does not contain information for query objects that are not part of a global namespace,
including entities and help. A base URL for an associated object is required to construct a complete query.
For entities, a base URL is retrieved for the service (domain, address, etc.) associated with a given entity.
The query URL is constructed by concatenating the base URL to the entity path segment specified in either
Sections or .
For help, a base URL is retrieved for any service (domain, address, etc.) for which additional information is
required. The query URL is constructed by concatenating the base URL to the help path segment specified in
.
A simple lookup to determine if an object exists (or not) without returning RDAP-encoded results
can be performed using the HTTP HEAD method as described in Section 4.1 of .
The resource type path segments for exact match lookup are:
'ip': Used to identify IP networks and associated data referenced using either an IPv4 or IPv6 address.
'autnum': Used to identify Autonomous System number registrations and associated data referenced using an asplain Autonomous System number.
'domain': Used to identify reverse DNS (RIR) or domain name (DNR) information and associated data referenced using a fully qualified domain name.
'nameserver': Used to identify a nameserver information query using a host name.
'entity': Used to identify an entity information query using a string identifier.
Syntax: ip/<IP address> or ip/<CIDR prefix>/<CIDR length>
Queries for information about IP networks are of the form /ip/XXX/... or /ip/XXX/YY/...
where the path segment following 'ip' is either an IPv4 dotted decimal or
IPv6 address (i.e., XXX) or an IPv4 or IPv6
Classless Inter-domain Routing (CIDR) notation address block (i.e., XXX/YY).
Semantically, the simpler form using the address can be thought of as a CIDR block with a bitmask length of 32 for IPv4
and a bitmask length of 128 for IPv6. A given specific address or CIDR may fall within multiple
IP networks in a hierarchy of networks; therefore, this query targets the "most-specific"
or smallest IP network that completely encompasses it in a hierarchy of IP networks.
The IPv4 and IPv6 address formats supported in this query are described in Section 3.2.2 of RFC 3986
as IPv4address and IPv6address ABNF definitions. Any valid IPv6 text address format
can be used. This includes IPv6 addresses written using with or without compressed zeros
and IPv6 addresses containing
embedded IPv4 addresses. The rules to write a text representation
of an IPv6 address are RECOMMENDED. However, the zone_id is
not appropriate in this context; therefore, the corresponding syntax extension in RFC 6874
MUST NOT be used, and servers are to ignore it if possible.
For example, the following URL would be used to find information for the most specific network containing 192.0.2.0:
https://example.com/rdap/ip/192.0.2.0
The following URL would be used to find information for the most specific network containing 192.0.2.0/24:
https://example.com/rdap/ip/192.0.2.0/24
The following URL would be used to find information for the most specific network containing 2001:db8::0:
https://example.com/rdap/ip/2001:db8::0
Syntax: autnum/<autonomous system number>
Queries for information regarding Autonomous System number registrations are of the form
/autnum/XXX/... where XXX is an asplain Autonomous System number. In some registries,
registration of Autonomous System numbers is done on an individual number basis, while
other registries may register blocks of Autonomous System numbers. The semantics of this
query are such that if a number falls within a range of registered blocks, the target of
the query is the block registration and that individual number registrations are considered
a block of numbers with a size of 1.
For example, the following URL would be used to find information describing Autonomous System
number 12 (a number within a range of registered blocks):
https://example.com/rdap/autnum/12
The following URL would be used to find information describing 4-byte Autonomous System number 65538:
https://example.com/rdap/autnum/65538
Syntax: domain/<domain name>
Queries for domain information are of the form /domain/XXXX/..., where XXXX is a
fully qualified (relative to the root) domain name (as specified in
and ) in either the
in-addr.arpa or ip6.arpa zones (for RIRs) or a fully qualified domain name in a
zone administered by the server operator (for DNRs). Internationalized Domain Names (IDNs)
represented in either A-label or U-label format are also
valid domain names. See for information on character
encoding for the U-label format.
IDNs SHOULD NOT be represented as a mixture of A-labels and U-labels; that is,
internationalized labels in an IDN SHOULD be either all A-labels or all U-labels. It is possible
for an RDAP client to assemble a query string from multiple independent data sources.
Such a client might not be able to perform conversions between A-labels and U-labels.
An RDAP server that receives a query string with a mixture of A-labels and U-labels MAY
convert all the U-labels to A-labels, perform IDNA processing, and proceed with exact-match
lookup. In such cases, the response to be returned to the query source may not match the
input from the query source. Alternatively, the server MAY refuse to process the query.
The server MAY perform the match using either the A-label or U-label form. Using one consistent
form for matching every label is likely to be more reliable.
The following URL would be used to find information describing the zone serving the network 192.0.2/24:
https://example.com/rdap/domain/2.0.192.in-addr.arpa
The following URL would be used to find information describing the zone serving the network 2001:db8:1::/48:
https://example.com/rdap/domain/1.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
The following URL would be used to find information for the blah.example.com domain name:
https://example.com/rdap/domain/blah.example.com
The following URL would be used to find information for thexn--fo-5ja.example IDN:
https://example.com/rdap/domain/xn--fo-5ja.example
Syntax: nameserver/<nameserver name>
The <nameserver name> parameter represents a fully qualified host name as specified in
and . Internationalized names represented
in either A-label or U-label format are also valid nameserver names.
IDN processing for nameserver names uses the domain name processing instructions specified in
. See for information on character encoding
for the U-label format.
The following URL would be used to find information for the ns1.example.com nameserver:
https://example.com/rdap/nameserver/ns1.example.com
The following URL would be used to find information for thens1.xn--fo-5ja.example nameserver:
https://example.com/rdap/nameserver/ns1.xn--fo-5ja.example
Syntax: entity/<handle>
The <handle> parameter represents an entity (such as a contact, registrant, or registrar)
identifier whose syntax is specific to the registration provider. For example, for some DNRs, contact
identifiers are specified in and .
The following URL would be used to find information for the entity associated with handle XXXX:
https://example.com/rdap/entity/XXXX
Syntax: help
The help path segment can be used to request helpful information (command syntax, terms of service,
privacy policy, rate-limiting policy, supported authentication methods, supported extensions, technical
support contact, etc.) from an RDAP server. The response to "help" should provide basic information
that a client needs to successfully use the service. The following URL would be used to return "help"
information:
https://example.com/rdap/help
Pattern matching semantics are described in .
The resource type path segments for search are:
'domains': Used to identify a domain name information search using a pattern to match a fully qualified domain name.
'nameservers': Used to identify a nameserver information search using a pattern to match a host name.
'entities': Used to identify an entity information search using a pattern to match a string identifier.
RDAP search path segments are formed using a concatenation of the plural form of the
object being searched for and an HTTP query string. The HTTP query string is formed using
a concatenation of the question mark character ('?', US-ASCII value 0x003F), the JSON object
value associated with the object being searched for, the equal sign character ('=', US-ASCII
value 0x003D), and the search pattern. Search pattern query processing is described more
fully in . For the domain, nameserver, and entity objects described in this
document, the plural object forms are "domains", "nameservers", and "entities".
Detailed results can be retrieved using the HTTP GET method and the path segments specified here.
Syntax: domains?name=<domain search pattern>
Syntax: domains?nsLdhName=<domain search pattern>
Syntax: domains?nsIp=<domain search pattern>
Searches for domain information by name are specified using this form:
domains?name=XXXX
XXXX is a search pattern representing a domain name in
"letters, digits, hyphen" (LDH) format in a zone administered by the server operator
of a DNR. The following URL would be used to find DNR information for domain names
matching the "example*.com" pattern:
https://example.com/rdap/domains?name=example*.com
IDNs in U-label format can
also be used as search patterns (see ). Searches for these
names are of the form /domains?name=XXXX, where XXXX is a search pattern representing
a domain name in U-label format. See
for information on character encoding for the U-label format.
Searches for domain information by nameserver name are specified using this form:
domains?nsLdhName=YYYY
YYYY is a search pattern representing a host name in
"letters, digits, hyphen" format in a zone administered by the server operator
of a DNR. The following URL would be used to search for domains delegated to nameservers
matching the "ns1.example*.com" pattern:
https://example.com/rdap/domains?nsLdhName=ns1.example*.com
Searches for domain information by nameserver IP address are specified using this form:
domains?nsIp=ZZZZ
ZZZZ is a search pattern representing an IPv4 or
IPv6 address. The following URL would be used to search
for domains that have been delegated to nameservers that resolve to the "192.0.2.0"
address:
https://example.com/rdap/domains?nsIp=192.0.2.0
Syntax: nameservers?name=<nameserver search pattern>
Syntax: nameservers?ip=<nameserver search pattern>
Searches for nameserver information by nameserver name are specified using this form:
nameservers?name=XXXX
XXXX is a search pattern representing a host name in
"letters, digits, hyphen" format in a zone administered by the server operator
of a DNR. The following URL would be used to find DNR information for nameserver
names matching the "ns1.example*.com" pattern:
https://example.com/rdap/nameservers?name=ns1.example*.com
Internationalized nameserver names in U-label format can
also be used as search patterns (see ). Searches for these
names are of the form /nameservers?name=XXXX, where XXXX is a search pattern representing
a nameserver name in U-label format. See
for information on character encoding for the U-label format.
Searches for nameserver information by nameserver IP address are specified using this form:
nameservers?ip=YYYY
YYYY is a search pattern representing an IPv4 or
IPv6 address. The following URL would be used to search
for nameserver names that resolve to the "192.0.2.0" address:
https://example.com/rdap/nameservers?ip=192.0.2.0
Syntax: entities?fn=<entity name search pattern>
Syntax: entities?handle=<entity handle search pattern>
Searches for entity information by name are specified using this form:
entities?fn=XXXX
XXXX is a search pattern representing the "FN" property of an entity (such as a
contact, registrant, or registrar) name as specified in Section 5.1 of
. The following URL would be used to find
information for entity names matching the "Bobby Joe*" pattern:
https://example.com/rdap/entities?fn=Bobby%20Joe*
Searches for entity information by handle are specified using this form:
entities?handle=XXXX
XXXX is a search pattern representing an entity (such as a contact, registrant, or
registrar) identifier whose syntax is specific to the registration provider. The following
URL would be used to find information for entity handles matching the "CID-40*" pattern:
https://example.com/rdap/entities?handle=CID-40*
URLs MUST be properly encoded according to the rules of .
In the example above, "Bobby Joe*" is encoded to "Bobby%20Joe*".
Servers indicate the success or failure of query processing by returning an appropriate HTTP
response code to the client. Response codes not specifically identified in this document are described
in .
Partial string searching uses the asterisk ('*', US-ASCII value 0x002A) character to match
zero or more trailing characters. A character string representing multiple domain name labels
MAY be concatenated to the end of the search pattern to limit the scope of the search. For example,
the search pattern "exam*" will match "example.com" and "example.net". The search pattern
"exam*.com" will match "example.com". If an asterisk appears in a search string, any label that
contains the non-asterisk characters in sequence plus zero or more characters in sequence in
place of the asterisk would match. Additional pattern matching processing is beyond the scope
of this specification.
If a server receives a search request but cannot process the request because it does not
support a particular style of partial match searching, it SHOULD return an HTTP 422 (Unprocessable Entity) response.
When returning a 422 error, the server MAY also return an error response body as specified
in Section 6 of if the requested media type
is one that is specified in .
Partial matching is not feasible across combinations of Unicode characters because
Unicode characters can be combined with each other. Servers SHOULD NOT partially match
combinations of Unicode characters where a legal combination is possible. It should be
noted, though, that it may not always be possible to detect cases where a character
could have been combined with another character, but was not, because characters can
be combined in many different ways.
Clients should avoid submitting a partial match search of Unicode characters where a Unicode
character may be legally combined with another Unicode character or characters.
Partial match searches with incomplete combinations of characters where a character
must be combined with another character or characters are invalid. Partial match
searches with characters that may be combined with another character or characters
are to be considered non-combined characters (that is, if character x may be combined
with character y but character y is not submitted in the search string, then
character x is a complete character and no combinations of character x are to be
searched).
Conceptually, any query-matching record in a server's database might be a member of a set of
related records, related in some fashion as defined by the server -- for example, variants of an IDN.
The entire set ought to be considered as candidates for inclusion when constructing the response.
However, the construction of the final response needs to be mindful of privacy and other
data-releasing policies when assembling the RDAP response set.
Note too that due to the nature of searching, there may be a list of query-matching records.
Each one of those is subject to being a member of a set as described in the previous paragraph.
What is ultimately returned in a response will be the union of all the sets that has been filtered
by whatever policies are in place.
Note that this model includes arrangements for associated names, including those that
are linked by policy mechanisms and names bound together for some other purposes. Note also that
returning information that was not explicitly selected by an exact-match lookup, including
additional names that match a relatively fuzzy search as well as lists of names that are linked
together, may cause privacy issues.
Note that there might not be a single, static information return policy that applies to all
clients equally. Client identity and associated authorizations can be a relevant factor in
determining how broad the response set will be for any particular query.
This document describes path segment specifications for a limited number of objects
commonly registered in both RIRs and DNRs. It does not attempt to describe path
segments for all of the objects registered in all registries. Custom path segments
can be created for objects not specified here using the process described in Section
6 of "HTTP Usage in the Registration Data Access Protocol (RDAP)"
.
Custom path segments can be created by prefixing the segment with a unique identifier
followed by an underscore character (0x5F). For example, a custom entity path
segment could be created by prefixing "entity" with "custom_", producing
"custom_entity". Servers MUST return an appropriate failure status code for a
request with an unrecognized path segment.
There is value in supporting the ability to submit either a U-label (Unicode form of
an IDN label) or an A-label (US-ASCII form of an IDN label) as a query argument to an
RDAP service. Clients capable of processing non-US-ASCII characters may prefer a U-label since this
is more visually recognizable and familiar than A-label strings, but clients using programmatic
interfaces might find it easier to submit and display A-labels if they are unable to input U-labels with
their keyboard configuration. Both query forms are acceptable.
Internationalized domain and nameserver names can contain character variants and
variant labels as described in . Clients that
support queries for internationalized domain and nameserver names MUST accept
service provider responses that describe variants as specified in "JSON Responses
for the Registration Data Access Protocol (RDAP)" .
Servers can expect to receive search patterns from clients that contain character strings
encoded in different forms supported by HTTP. It is entirely possible to apply filters and
normalization rules to search patterns prior to making character comparisons, but this type
of processing is more typically needed to determine the validity of registered strings than
to match patterns.
An RDAP client submitting a query string containing non-US-ASCII characters converts
such strings into Unicode in UTF-8 encoding. It then performs any local case mapping deemed
necessary. Strings are normalized using Normalization Form C (NFC) ;
note that clients might not be able to do this reliably. UTF-8 encoded strings are then
appropriately percent-encoded in the query URL.
After parsing any percent-encoding, an RDAP server treats each query string as Unicode in
UTF-8 encoding. If a string is not valid UTF-8, the server can immediately stop processing the
query and return an HTTP 400 (Bad Request) response.
When processing queries, there is a difference in handling DNS names, including those with
putative U-labels, and everything else. DNS names are treated according to the DNS matching rules
as described in Section 3.1 of RFC 1035 for Non-Reserved LDH (NR-LDH) labels and the matching
rules described in Section 5.4 of RFC 5891 for U-labels. Matching of DNS
names proceeds one label at a time because it is possible for a combination of U-labels and NR&nbhy;LDH
labels to be found in a single domain or host name. The determination of whether a label is a U-label
or an NR&nbhy;LDH label is based on whether the label contains any characters outside of the US&nbhy;ASCII
letters, digits, or hyphen (the so-called LDH rule).
For everything else, servers map fullwidth and halfwidth characters to their decomposition equivalents.
Servers convert strings to the same coded character set of the target data that is to be looked up or
searched, and each string is normalized using the same normalization that was used on the target data.
In general, storage of strings as Unicode is RECOMMENDED. For the purposes of comparison, Normalization
Form KC (NFKC) with case folding is used to maximize predictability and
the number of matches. Note the use of case-folded NFKC as opposed to NFC in this case.
Security services for the operations specified in this document are described in "Security Services for the
Registration Data Access Protocol (RDAP)" .
Search functionality typically requires more server resources (such as memory, CPU cycles, and
network bandwidth) when compared to basic lookup functionality. This increases the risk of server
resource exhaustion and subsequent denial of service due to abuse. This risk can be mitigated by
developing and implementing controls to restrict search functionality to identified and authorized
clients. If those clients behave badly, their search privileges can be suspended or revoked. Rate
limiting as described in Section 5.5 of "HTTP Usage in the Registration Data Access Protocol (RDAP)"
can also be used to control the rate of received search
requests. Server operators can also reduce their risk by restricting the amount of information returned
in response to a search request.
Search functionality also increases the privacy risk of disclosing object relationships that might
not otherwise be obvious. For example, a search that returns IDN variants that do not
explicitly match a client-provided search pattern can disclose information about registered domain
names that might not be otherwise available. Implementers need to consider the policy and privacy implications of
returning information that was not explicitly requested.
Note that there might not be a single, static information return policy that applies to all
clients equally. Client identity and associated authorizations can be a relevant factor in
determining how broad the response set will be for any particular query.
Finding the Authoritative Registration Data (RDAP) Service
JSON Responses for the Registration Data Access Protocol (RDAP)
Security Services for the Registration Data Access Protocol (RDAP)
HTTP Usage in the Registration Data Access Protocol (RDAP)
Unicode Standard Annex #15: Unicode Normalization Forms
The Unicode Consortium
Architectural Styles and the Design of Network-based Software Architectures
University of California, Irvine
This document is derived from original work on RIR query formats developed by Byron J. Ellacott of APNIC,
Arturo L. Servin of LACNIC, Kaveh Ranjbar of the RIPE NCC, and Andrew L. Newton of ARIN. Additionally, this
document incorporates DNR query formats originally described by Francisco Arias and Steve Sheng of ICANN
and Scott Hollenbeck of Verisign Labs.
The authors would like to acknowledge the following individuals for their contributions to this document:
Francisco Arias, Marc Blanchet, Ernie Dainow, Jean-Philippe Dionne, Byron J. Ellacott, Behnam Esfahbod, John Klensin,
John Levine, Edward Lewis, Mark Nottingham, Kaveh Ranjbar, Arturo L. Servin, Steve Sheng, and Andrew Sullivan.