Network Working Group                                        A.L. Newton
Internet-Draft                                                      ARIN
Intended status: Standards Track                           B.J. Ellacott
Expires: October 17, 2013                                          APNIC
                                                                 N. Kong
                                                          April 17, 2013

       HTTP usage in the Registration Data Access Protocol (RDAP)


   This document is one of a collection that together describe the
   Registration Data Access Protocol (RDAP).  It describes how RDAP is
   transported using the Hypertext Transfer Protocol (HTTP).

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on October 17, 2013.

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   provided without warranty as described in the Simplified BSD License.

1.  Introduction

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   This document describes the usage of HTTP for Registration Data
   Directory Services.  The goal of this document is to tie together
   usage patterns of HTTP into a common profile applicable to the
   various types of Directory Services serving Registration Data using
   RESTful practices.  By giving the various Directory Services common
   behavior, a single client is better able to retrieve data from
   Directory Services adhering to this behavior.

   The registration data expected to be presented by this service is
   Internet resource registration data - registration of domain names
   and Internet number resources.  This data is typically provided by
   WHOIS [RFC3912] services, but the WHOIS protocol is insufficient to
   modern registration data service requirements.  A replacement
   protocol is expected to retain the simple transactional nature of
   WHOIS, while providing a specification for queries and responses,
   redirection to authoritative sources, support for Internationalized
   Domain Names (IDNs, [RFC5890]), and support for localized
   registration data such as addresses and organisation or person names.

   In designing these common usage patterns, this document introduces
   considerations for a simple use of HTTP.  Where complexity may
   reside, it is the goal of this document to place it upon the server
   and to keep the client as simple as possible.  A client
   implementation should be possible using common operating system
   scripting tools.

   This is the basic usage pattern for this protocol:

   1.  A client issues an HTTP query using GET. As an example, a query
       for the network registration might be http://

   2.  If the receiving server has the information for the query, it
       examines the Accept header field of the query and returns a 200
       response with a response entity appropriate for the requested

   3.  If the receiving server does not have the information for the
       query but does have knowledge of where the information can be
       found, it will return a redirection response (3xx) with the
       Location: header field containing an HTTP(S) URL (Uniform
       Resource Locator) pointing to the information or another server
       known to have knowledge of the location of the information.  The
       client is expected to re-query using that HTTP URL.

   4.  If the receiving server does not have the information being
       requested and does not have knowledge of where the information
       can be found, it returns a 404 response.

   5.  If the receiving server will not answer a request for policy
       reasons, it will return an error response (4xx) indicating the
       reason for giving no answer.

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   It is important to note that it is not the intent of this document to
   redefine the meaning and semantics of HTTP. The purpose of this
   document is to clarify the use of standard HTTP mechanisms for this

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

   As is noted in SSAC Report on WHOIS Terminology and Structure
   [SAC-051], the term "WHOIS" is overloaded, often referring to a
   protocol, a service and data.  In accordance with [SAC-051], this
   document describes the base behavior for a Registration Data Access
   Protocol (RDAP).  [SAC-051] describes a protocol profile of RDAP for
   Domain Name Registries (DNRs), the Domain Name Registration Data
   Access Protocol (DNRD-AP).

   In this document, an RDAP client is an HTTP User Agent performing an
   RDAP query, and an RDAP server is an HTTP server providing an RDAP
   response.  RDAP query and response formats are described in other
   documents in the collection of RDAP specifications, while this
   document describes how RDAP clients and servers use HTTP to exchange
   queries and responses.

3.  Design Intents

   There are a few design criteria this document attempts to meet.

   First, each query is meant to return either zero or one result.  With
   the maximum upper bound being set to one, the issuance of redirects
   is simplified to the known query/response model used by HTTP
   [RFC2616].  Should an entity contain more than one result, some of
   which are better served by other servers, the redirection model
   becomes much more complicated.

   Second, multiple response formats are supported by this protocol.  At
   present the IETF WEIRDS working group is defining only a JSON
   [RFC4627] response format, but server operators may use other data
   formats when those formats are requested.

   Third, this protocol is intended to be able to make use of the range
   of mechanisms available for use with HTTP.  HTTP offers a number of
   mechanisms not described further in this document.  Operators are
   able to make use of these mechanisms according to their local policy,
   including cache control, authorization, compression, and redirection.
   HTTP also benefits from widespread investment in scalability,
   reliability, and performance, and widespread programmer understanding
   of client behaviours for RESTful web services, reducing the cost to
   deploy Registration Data Directory Services and clients.

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4.  Queries

4.1.  Accept Header

   RDAP clients MUST include an Accept: header field specifying
   application/rdap+json, application/json, or both.  Servers receiving
   an RDAP request MUST return an entity with Content-Type application/

   This specification does not define the responses a server returns to
   a request with any other media types in the Accept: header field, or
   with no Accept: header field.  One possibility would be to return a
   response in a media type suitable for rendering in a web browser.

4.2.  Query Parameters

   Servers MUST ignore unknown query parameters.  Use of unknown query
   parameters for cache-busting is described in Appendix Appendix B.

5.  Types of HTTP Response

   This section describes the various types of responses a server may
   send to a client.  While no standard HTTP response code is forbidden
   in usage, at a minimum clients SHOULD understand the response codes
   described in this section.  It is expected that usage of response
   codes and types for this application not defined here will be
   described in subsequent documents.

5.1.  Positive Answers

   If a server has the information requested by the client and wishes to
   respond to the client with the information according to its policies,
   it encodes the answer in the format most appropriate according to the
   standard and defined rules for processing the HTTP Accept header
   field, and return that answer in the body of a 200 response.

5.2.  Redirects

   If a server wishes to inform a client that the answer to a given
   query can be found elsewhere, it MUST return a 301 response code to
   indicate a permanent move, or a 307 response code to indicate a non-
   permanent redirection, and include an HTTP(s) URL in the Location:
   header field.  The client is expected to issue a subsequent request
   to satisfy the original query using the given URL without any
   processing of the URL.  In other words, the server is to hand back a
   complete URL and the client should not have to transform the URL to
   follow it.

   For this application, such an example of a permanent move might be a
   Top Level Domain (TLD) operator informing a client the information
   being sought can be found with another TLD operator (i.e.  a query
   for the domain bar in foo.example is found at http://foo.example/

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   For example, if the client sends
   domain/, the server redirecting to https:// would set the Location: field to the

5.3.  Negative Answers

   If a server wishes to respond that it has no information regarding
   the query, it MUST return a 404 response code.  Optionally, it MAY
   include additional information regarding the negative answer in the
   HTTP entity body.

   If a server wishes to inform the client that information about the
   query is available, but cannot include the information in the
   response to the client for policy reasons, the server MUST respond
   with an appropriate response code out of HTTP's 4xx range.  Clients
   MAY retry the query based on the respective response code.

5.4.  Malformed Queries

   If a server receives a query which it cannot interpret as an RDAP
   query, it MUST return a 400 response code.  Optionally, it MAY
   include additional information regarding this negative answer in the
   HTTP entity body.

5.5.  Rate Limits

   Some servers apply rate limits to deter address scraping and other
   abuses.  When a server declines to answer a query due to rate limits,
   it SHOULD return a 429 response code as described in [RFC6585].  A
   client that receives a 429 response SHOULD decrease its query rate,
   and honor the Retry-After header field if one is present.

   Note that this is not a defense against denial-of-service attacks,
   since a malicious client could ignore the code and continue to send
   queries at a high rate.  A server might use another response code if
   it did not wish to reveal to a client that rate limiting is the
   reason for the denial of a reply.

5.6.  Cross-Origin Resource Sharing

   When responding to queries, it is RECOMMENDED that servers use the
   Access-Control-Allow-Origin header field, as specified by [W3C.CR-

6.  Extensibility

   For extensibility purposes, this document defines an IANA registry
   for prefixes used in JSON [RFC4627] data serialization and URI path
   segments (see Section 8).

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   Prefixes and identifiers SHOULD only consist of the alphabetic ASCII
   characters A through Z in both uppercase and lowercase, the numerical
   digits 0 through 9, underscore characters, and SHOULD NOT begin with
   an underscore character, numerical digit or the characters "xml".
   The following describes the production of JSON names in ABNF

   ABNF for JSON names

     name = ALPHA *( ALPHA / DIGIT / "_" )

   This restriction is a union of the Ruby programming language
   identifier syntax and the XML element name syntax and has two
   purposes.  First, client implementers using modern programming
   languages such as Ruby or Java can use libraries that automatically
   promote JSON names to first order object attributes or members.
   Second, a clean mapping between JSON and XML is easy to accomplish
   using these rules.

7.  Security Considerations

   This document does not pose strong security requirements to the RDAP
   protocol.  However, it does not restrict against the use of security
   mechanisms offered by the HTTP protocol.

   This document made recommendations for server implementations against
   denial-of-service (Section 5.5) and interoperability with existing
   security mechanism in HTTP clients (Section 5.6).

   Additional security considerations to the RDAP protocol will be
   covered in future RFCs documenting specific security mechanisms and

8.  IANA Considerations

8.1.  RDAP Extensions Registry

   This specification proposes an IANA registry for RDAP extensions.
   The purpose of this registry is to ensure uniqueness of extension
   identifiers.  The extension identifier is used as a prefix in JSON
   names and as a prefix of path segments in RDAP URLs.

   The production rule for these identifiers is specified in Section 6.

   In accordance with RFC5226, the IANA policy for assigning new values
   shall be Specification Required: values and their meanings must be
   documented in an RFC or in some other permanent and readily available
   reference, in sufficient detail that interoperability between
   independent implementations is possible.

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   The following is a preliminary template for an RDAP extension

      Extension identifier: the identifier of the extension

      Registry operator: the name of the registry operator

      Published specification: RFC number, bibliographical reference or
      URL to a permanent and readily available specification

      Person & email address to contact for further information: The
      names and email addresses of individuals for contact regarding
      this registry entry

      Intended usage: brief reasons for this registry entry

   The following is an example of a registration in the RDAP extension

      Extension identifier: lunarNic

      Registry operator: The Registry of the Moon, LLC

      Published specification: http://www.example/moon_apis/rdap

      Person & email address to contact for further information:
      Professor Bernardo de la Paz <berny@moon.example>

      Intended usage: COMMON

8.2.  RDAP Media Type Registration

   This specification registers the "application/rdap+json" media type.

      Type name: application

      Subtype name: rdap+json

      Required parameters: n/a

      Encoding considerations: n/a

      Security considerations: n/a

      Interoperability considerations: n/a

      Published specification: [[ this document ]]

      Applications that use this media type: RDAP

      Additional information: n/a

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      Person & email address to contact for further information: Andy
      Newton <>

      Intended usage: COMMON

      Restrictions on usage: none

      Author: Andy Newton

      Change controller: IETF

      Provisional Registration: Yes

9.  Internationalization Considerations

9.1.  URIs and IRIs

   Clients MAY use IRIs [RFC3987] as they see fit, but MUST transform
   them to URIs [RFC3986] for interaction with RDAP servers.  RDAP
   servers MUST use URIs in all responses, and clients MAY transform
   these URIs to IRIs.

9.2.  Language Identifiers in Queries and Responses

   Under most scenarios, clients requesting data will not signal that
   the data be returned in a particular language or script.  On the
   other hand, when servers return data and have knowledge that the data
   is in a language or script, the data SHOULD be annotated with
   language identifiers whenever they are available, thus allowing
   clients to process and display the data accordingly.

   The mechanism for including a language identifier in a response will
   be defined in subsequent documents describing specific response

9.3.  Language Identifiers in HTTP Headers

   Given the description of the use of language identifiers in Section
   9.2, unless otherwise specified servers SHOULD ignore the HTTP
   [RFC2616] Accept-Language header field when formulating HTTP entity
   responses, so that clients do not conflate the Accept-Language header
   with the 'lang' values in the entity body.

   However, servers MAY return language identifiers in the Content-
   Language header field so as to inform clients of the intended
   language of HTTP layer messages.

10.  Contributing Authors and Acknowledgements

   John Levine provided text to tighten up the Accept header field usage
   and the text for the section on 429 responses.

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   Marc Blanchet provided some clarifying text regarding the use of URLs
   with redirects, as well as very useful feedback during WGLC.

   Normative language reviews were provided by Murray S. Kucherawy and
   Andrew Sullivan.

   Jean-Phillipe Dionne provided text for the Security Considerations

11.  References

   [SAC-051]  Piscitello, D., Ed., "SSAC Report on Domain Name WHOIS
              Terminology and Structure", September 2011.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [RFC3912]  Daigle, L., "WHOIS Protocol Specification", RFC 3912,
              September 2004.

   [RFC3986]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [RFC5890]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              RFC 5890, August 2010.

   [RFC6585]  Nottingham, M. and R. Fielding, "Additional HTTP Status
              Codes", RFC 6585, April 2012.

              Kesteren, A., "Cross-Origin Resource Sharing", World Wide
              Web Consortium Candidate Recommendation CR-cors-20130129,
              January 2013, <

Appendix A.  Protocol Example

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   To demonstrate typical behaviour of an RDAP client and server, the
   following is an example of an exchange, including a redirect.  The
   data in the response has been elided for brevity, as the data format
   is not described in this document.

   An example of an RDAP client and server exchange:

         <TCP connect to port 80>
         GET /ip/ HTTP/1.1
         Accept: application/rdap+json
         HTTP 301 Moved Permanently
         Content-Length: 0
         Content-Type: application/rdap+json; charset=UTF-8
         <TCP disconnect>

         <TCP connect to port 80>
         GET /ip/ HTTP/1.1
         Accept: application/rdap+json
         HTTP 200 OK
         Content-Type: application/rdap_json; charset=UTF-8
         Content-Length: 9001

         { ... }
         <TCP disconnect>

Appendix B.  Cache Busting

   Some HTTP [RFC2616] cache infrastructure does not adhere to caching
   standards adequately, and could cache responses longer than is
   intended by the server.  To overcome these issues, clients MAY use an
   adhoc and improbably used query parameter with a random value of
   their choosing.  As Section 4.2 instructs servers to ignore unknown
   parameters, this is unlikely to have any known side effects.

   An example of using an unknown query parameter to bust caches:

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   Use of an unknown parameter to overcome misbehaving caches is not
   part of any specification and is offered here for informational

Appendix C.  Changelog

   Initial WG -00: Updated to working group document 2012-September-20


      *  Updated for the sections moved to the JSON responses draft.

      *  Simplified media type, removed "level" parameter.

      *  Updated 2119 language and added boilerplate.

      *  In section 1, noted that redirects can go to redirect servers
         as well.

      *  Added Section 9.2 and Section 9.3.


      *  Added a section on 429 response codes.

      *  Changed Accept header language in section 4.1

      *  Removed reference to the now dead requirements draft.

      *  Added contributing authors and acknowledgements section.

      *  Added some clarifying text regarding complete URLs in the
         redirect section.

      *  Changed media type to application/rdap+json

      *  Added media type registration


      *  Removed forward reference to draft-ietf-weirds-json-response.

      *  Added reference and recommended usage of CORS


      *  Revised introduction and abstract.

      *  Added negative responses other than 404.

      *  Added security considerations.

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      *  Added and corrected references: CORS, RFC3912, RFC3987,

      *  Expanded on first use several acronyms.

      *  Updated 2119 language.

Authors' Addresses

   Andrew Lee Newton
   American Registry for Internet Numbers
   3635 Concorde Parkway
   Chantilly, VA 20151


   Byron J. Ellacott
   Asia Pacific Network Information Center
   6 Cordelia Street
   South Brisbane QLD 4101


   Ning Kong
   China Internet Network Information Center
   4 South 4th Street, Zhongguancun, Haidian District
   Beijing 100190

   Phone: +86 10 5881 3147

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