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rfc:rfc7482

Internet Engineering Task Force (IETF) A. Newton Request for Comments: 7482 ARIN Category: Standards Track S. Hollenbeck ISSN: 2070-1721 Verisign Labs

                                                            March 2015
       Registration Data Access Protocol (RDAP) Query Format

Abstract

 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).

Status of This Memo

 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 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7482.

Copyright Notice

 Copyright (c) 2015 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Newton & Hollenbeck Standards Track [Page 1] RFC 7482 RDAP Query Format March 2015

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Conventions Used in This Document . . . . . . . . . . . . . .   4
   2.1.  Acronyms and Abbreviations  . . . . . . . . . . . . . . .   4
 3.  Path Segment Specification  . . . . . . . . . . . . . . . . .   4
   3.1.  Lookup Path Segment Specification . . . . . . . . . . . .   5
     3.1.1.  IP Network Path Segment Specification . . . . . . . .   6
     3.1.2.  Autonomous System Path Segment Specification  . . . .   7
     3.1.3.  Domain Path Segment Specification . . . . . . . . . .   7
     3.1.4.  Nameserver Path Segment Specification . . . . . . . .   8
     3.1.5.  Entity Path Segment Specification . . . . . . . . . .   9
     3.1.6.  Help Path Segment Specification . . . . . . . . . . .   9
   3.2.  Search Path Segment Specification . . . . . . . . . . . .   9
     3.2.1.  Domain Search . . . . . . . . . . . . . . . . . . . .  10
     3.2.2.  Nameserver Search . . . . . . . . . . . . . . . . . .  11
     3.2.3.  Entity Search . . . . . . . . . . . . . . . . . . . .  12
 4.  Query Processing  . . . . . . . . . . . . . . . . . . . . . .  13
   4.1.  Partial String Searching  . . . . . . . . . . . . . . . .  13
   4.2.  Associated Records  . . . . . . . . . . . . . . . . . . .  14
 5.  Extensibility . . . . . . . . . . . . . . . . . . . . . . . .  14
 6.  Internationalization Considerations . . . . . . . . . . . . .  15
   6.1.  Character Encoding Considerations . . . . . . . . . . . .  15
 7.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
 8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
   8.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
   8.2.  Informative References  . . . . . . . . . . . . . . . . .  19
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  19
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1. Introduction

 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)
 [RFC7230] and the conventions described in [RFC7480].  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 [RFC3912] that have been
 identified over time, including:
 o  lack of standardized command structures;
 o  lack of standardized output and error structures;
 o  lack of support for internationalization and localization; and

Newton & Hollenbeck Standards Track [Page 2] RFC 7482 RDAP Query Format March 2015

 o  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:
 o  networks by IP address;
 o  Autonomous System (AS) numbers by number;
 o  reverse DNS metadata by domain;
 o  nameservers by name;
 o  registrars by name; and
 o  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) [RFC7231] 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 Section 5 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
 [RFC3986] patterns specified in this document are only applicable to
 the HTTP [RFC7231] 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 [RFC7483].
 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.

Newton & Hollenbeck Standards Track [Page 3] RFC 7482 RDAP Query Format March 2015

 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 [RFC7481].

2. Conventions Used in This Document

 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 [RFC2119].

2.1. Acronyms and Abbreviations

    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 [Unicode-UAX15]
    NFKC: Unicode Normalization Form KC [Unicode-UAX15]
    RDAP: Registration Data Access Protocol
    REST: Representational State Transfer.  The term was first
    described in a doctoral dissertation [REST].
    RESTful: An adjective that describes a service using HTTP and the
    principles of REST.
    RIR: Regional Internet Registry

3. Path Segment Specification

 The base URLs used to construct RDAP queries are maintained in an
 IANA registry described in [RFC7484].  Queries are formed by
 retrieving an appropriate base URL from the registry and appending a
 path segment specified in either Sections 3.1 or 3.2.  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

Newton & Hollenbeck Standards Track [Page 4] RFC 7482 RDAP Query Format March 2015

 of RFC 3986 [RFC3986].  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 3.1.5 or 3.2.3.
 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 Section 3.1.6.

3.1. Lookup Path Segment Specification

 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 [RFC7480].
 The resource type path segments for exact match lookup are:
 o  'ip': Used to identify IP networks and associated data referenced
    using either an IPv4 or IPv6 address.
 o  'autnum': Used to identify Autonomous System number registrations
    and associated data referenced using an asplain Autonomous System
    number.
 o  'domain': Used to identify reverse DNS (RIR) or domain name (DNR)
    information and associated data referenced using a fully qualified
    domain name.
 o  'nameserver': Used to identify a nameserver information query
    using a host name.
 o  'entity': Used to identify an entity information query using a
    string identifier.

Newton & Hollenbeck Standards Track [Page 5] RFC 7482 RDAP Query Format March 2015

3.1.1. IP Network Path Segment Specification

 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 [RFC5952] address (i.e., XXX) or an IPv4
 or IPv6 Classless Inter-domain Routing (CIDR) [RFC4632] 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 [RFC3986] as IPv4address and
 IPv6address ABNF definitions.  Any valid IPv6 text address format
 [RFC4291] 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 [RFC5952] are RECOMMENDED.  However, the zone_id
 [RFC4007] is not appropriate in this context; therefore, the
 corresponding syntax extension in RFC 6874 [RFC6874] 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

Newton & Hollenbeck Standards Track [Page 6] RFC 7482 RDAP Query Format March 2015

3.1.2. Autonomous System Path Segment Specification

 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 [RFC5396].  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

3.1.3. Domain Path Segment Specification

 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 [RFC0952] and [RFC1123]) 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 [RFC5890] are also valid domain names.  See
 Section 6.1 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

Newton & Hollenbeck Standards Track [Page 7] RFC 7482 RDAP Query Format March 2015

 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 the
 xn--fo-5ja.example IDN:
 https://example.com/rdap/domain/xn--fo-5ja.example

3.1.4. Nameserver Path Segment Specification

 Syntax: nameserver/<nameserver name>
 The <nameserver name> parameter represents a fully qualified host
 name as specified in [RFC0952] and [RFC1123].  Internationalized
 names represented in either A-label or U-label format [RFC5890] are
 also valid nameserver names.  IDN processing for nameserver names
 uses the domain name processing instructions specified in
 Section 3.1.3.  See Section 6.1 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

Newton & Hollenbeck Standards Track [Page 8] RFC 7482 RDAP Query Format March 2015

 The following URL would be used to find information for the
 ns1.xn--fo-5ja.example nameserver:
 https://example.com/rdap/nameserver/ns1.xn--fo-5ja.example

3.1.5. Entity Path Segment Specification

 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 [RFC5730] and [RFC5733].
 The following URL would be used to find information for the entity
 associated with handle XXXX:
 https://example.com/rdap/entity/XXXX

3.1.6. Help Path Segment Specification

 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

3.2. Search Path Segment Specification

 Pattern matching semantics are described in Section 4.1.  The
 resource type path segments for search are:
 o  'domains': Used to identify a domain name information search using
    a pattern to match a fully qualified domain name.
 o  'nameservers': Used to identify a nameserver information search
    using a pattern to match a host name.
 o  'entities': Used to identify an entity information search using a
    pattern to match a string identifier.

Newton & Hollenbeck Standards Track [Page 9] RFC 7482 RDAP Query Format March 2015

 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 Section 4.
 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.

3.2.1. Domain Search

 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 [RFC5890] 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 [RFC5890] can also be used as search patterns
 (see Section 4).  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 [RFC5890].  See Section 6.1 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

Newton & Hollenbeck Standards Track [Page 10] RFC 7482 RDAP Query Format March 2015

 YYYY is a search pattern representing a host name in "letters,
 digits, hyphen" format [RFC5890] 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 [RFC1166] or IPv6
 [RFC5952] 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

3.2.2. Nameserver Search

 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 [RFC5890] 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 [RFC5890] can
 also be used as search patterns (see Section 4).  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 [RFC5890].
 See Section 6.1 for information on character encoding for the U-label
 format.

Newton & Hollenbeck Standards Track [Page 11] RFC 7482 RDAP Query Format March 2015

 Searches for nameserver information by nameserver IP address are
 specified using this form:
 nameservers?ip=YYYY
 YYYY is a search pattern representing an IPv4 [RFC1166] or IPv6
 [RFC5952] 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

3.2.3. Entity Search

 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 [RFC7483].  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 [RFC3986].
 In the example above, "Bobby Joe*" is encoded to "Bobby%20Joe*".

Newton & Hollenbeck Standards Track [Page 12] RFC 7482 RDAP Query Format March 2015

4. Query Processing

 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
 [RFC7480].

4.1. Partial String Searching

 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)
 [RFC4918] response.  When returning a 422 error, the server MAY also
 return an error response body as specified in Section 6 of [RFC7483]
 if the requested media type is one that is specified in [RFC7480].
 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).

Newton & Hollenbeck Standards Track [Page 13] RFC 7482 RDAP Query Format March 2015

4.2. Associated Records

 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.

5. Extensibility

 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)" [RFC7480].
 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.

Newton & Hollenbeck Standards Track [Page 14] RFC 7482 RDAP Query Format March 2015

6. Internationalization Considerations

 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 [RFC4290].  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)" [RFC7483].

6.1. Character Encoding Considerations

 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) [Unicode-UAX15]; note
 that clients might not be able to do this reliably.  UTF-8 encoded
 strings are then appropriately percent-encoded [RFC3986] 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 [RFC1035] for Non-Reserved LDH (NR-LDH)
 labels and the matching rules described in Section 5.4 of RFC 5891
 [RFC5891] 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-LDH labels to be found in a single domain or host name.  The

Newton & Hollenbeck Standards Track [Page 15] RFC 7482 RDAP Query Format March 2015

 determination of whether a label is a U-label or an NR-LDH label is
 based on whether the label contains any characters outside of the
 US-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) [Unicode-UAX15] 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.

7. Security Considerations

 Security services for the operations specified in this document are
 described in "Security Services for the Registration Data Access
 Protocol (RDAP)" [RFC7481].
 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)" [RFC7480] 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 [RFC6927] 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.

Newton & Hollenbeck Standards Track [Page 16] RFC 7482 RDAP Query Format March 2015

8. References

8.1. Normative References

 [RFC0952]  Harrenstien, K., Stahl, M., and E. Feinler, "DoD Internet
            host table specification", RFC 952, October 1985,
            <http://www.rfc-editor.org/info/rfc952>.
 [RFC1035]  Mockapetris, P., "Domain names - implementation and
            specification", STD 13, RFC 1035, November 1987,
            <http://www.rfc-editor.org/info/rfc1035>.
 [RFC1123]  Braden, R., Ed., "Requirements for Internet Hosts -
            Application and Support", STD 3, RFC 1123, October 1989,
            <http://www.rfc-editor.org/info/rfc1123>.
 [RFC1166]  Kirkpatrick, S., Stahl, M., and M. Recker, "Internet
            numbers", RFC 1166, July 1990,
            <http://www.rfc-editor.org/info/rfc1166>.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
            Resource Identifier (URI): Generic Syntax", STD 66, RFC
            3986, January 2005,
            <http://www.rfc-editor.org/info/rfc3986>.
 [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
            Architecture", RFC 4291, February 2006,
            <http://www.rfc-editor.org/info/rfc4291>.
 [RFC4632]  Fuller, V. and T. Li, "Classless Inter-domain Routing
            (CIDR): The Internet Address Assignment and Aggregation
            Plan", BCP 122, RFC 4632, August 2006,
            <http://www.rfc-editor.org/info/rfc4632>.
 [RFC4918]  Dusseault, L., Ed., "HTTP Extensions for Web Distributed
            Authoring and Versioning (WebDAV)", RFC 4918, June 2007,
            <http://www.rfc-editor.org/info/rfc4918>.
 [RFC5396]  Huston, G. and G. Michaelson, "Textual Representation of
            Autonomous System (AS) Numbers", RFC 5396, December 2008,
            <http://www.rfc-editor.org/info/rfc5396>.

Newton & Hollenbeck Standards Track [Page 17] RFC 7482 RDAP Query Format March 2015

 [RFC5730]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
            STD 69, RFC 5730, August 2009,
            <http://www.rfc-editor.org/info/rfc5730>.
 [RFC5733]  Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
            Contact Mapping", STD 69, RFC 5733, August 2009,
            <http://www.rfc-editor.org/info/rfc5733>.
 [RFC5890]  Klensin, J., "Internationalized Domain Names for
            Applications (IDNA): Definitions and Document Framework",
            RFC 5890, August 2010,
            <http://www.rfc-editor.org/info/rfc5890>.
 [RFC5891]  Klensin, J., "Internationalized Domain Names in
            Applications (IDNA): Protocol", RFC 5891, August 2010,
            <http://www.rfc-editor.org/info/rfc5891>.
 [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
            Address Text Representation", RFC 5952, August 2010,
            <http://www.rfc-editor.org/info/rfc5952>.
 [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
            Protocol (HTTP/1.1): Message Syntax and Routing", RFC
            7230, June 2014, <http://www.rfc-editor.org/info/rfc7230>.
 [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
            Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
            June 2014, <http://www.rfc-editor.org/info/rfc7231>.
 [RFC7480]  Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
            Registration Data Access Protocol (RDAP)", RFC 7480, March
            2015, <http://www.rfc-editor.org/info/rfC7480>.
 [RFC7481]  Hollenbeck, S. and N. Kong, "Security Services for the
            Registration Data Access Protocol (RDAP)", RFC 7481, March
            2015, <http://www.rfc-editor.org/info/rfc7481>.
 [RFC7483]  Newton, A. and S. Hollenbeck, "JSON Responses for the
            Registration Data Access Protocol (RDAP)", RFC 7483, March
            2015, <http://www.rfc-editor.org/info/rfc7483>.
 [RFC7484]  Blanchet, M., "Finding the Authoritative Registration Data
            (RDAP) Service", RFC 7484, March 2015,
            <http://www.rfc-editor.org/info/rfc7484>.

Newton & Hollenbeck Standards Track [Page 18] RFC 7482 RDAP Query Format March 2015

 [Unicode-UAX15]
            The Unicode Consortium, "Unicode Standard Annex #15:
            Unicode Normalization Forms", September 2013,
            <http://www.unicode.org/reports/tr15/>.

8.2. Informative References

 [REST]     Fielding, R., "Architectural Styles and the Design of
            Network-based Software Architectures", Ph.D. Dissertation,
            University of California, Irvine, 2000,
            <http://www.ics.uci.edu/~fielding/pubs/dissertation/
            fielding_dissertation.pdf>.
 [RFC3912]  Daigle, L., "WHOIS Protocol Specification", RFC 3912,
            September 2004, <http://www.rfc-editor.org/info/rfc3912>.
 [RFC4007]  Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
            B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
            March 2005, <http://www.rfc-editor.org/info/rfc4007>.
 [RFC4290]  Klensin, J., "Suggested Practices for Registration of
            Internationalized Domain Names (IDN)", RFC 4290, December
            2005, <http://www.rfc-editor.org/info/rfc4290>.
 [RFC6874]  Carpenter, B., Cheshire, S., and R. Hinden, "Representing
            IPv6 Zone Identifiers in Address Literals and Uniform
            Resource Identifiers", RFC 6874, February 2013,
            <http://www.rfc-editor.org/info/rfc6874>.
 [RFC6927]  Levine, J. and P. Hoffman, "Variants in Second-Level Names
            Registered in Top-Level Domains", RFC 6927, May 2013,
            <http://www.rfc-editor.org/info/rfc6927>.

Acknowledgements

 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.

Newton & Hollenbeck Standards Track [Page 19] RFC 7482 RDAP Query Format March 2015

Authors' Addresses

 Andrew Lee Newton
 American Registry for Internet Numbers
 3635 Concorde Parkway
 Chantilly, VA  20151
 United States
 EMail: andy@arin.net
 URI:   http://www.arin.net
 Scott Hollenbeck
 Verisign Labs
 12061 Bluemont Way
 Reston, VA  20190
 United States
 EMail: shollenbeck@verisign.com
 URI:   http://www.verisignlabs.com/

Newton & Hollenbeck Standards Track [Page 20]

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