Network Working Group                                        A.L. Newton
Internet-Draft                                                      ARIN
Intended status: Standards Track                           B.J. Ellacott
Expires: September 28, 2013                                        APNIC
                                                                 N. Kong
                                                          March 27, 2013

      Using the Registration Data Access Protocol (RDAP) with HTTP


   This document describes the usage of the Registration Data Access
   Protocol (RDAP) using HTTP.

Status of This Memo

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   This Internet-Draft will expire on September 28, 2013.

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1.  Introduction

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

   In designing these common usage patterns, this draft endeavours to
   satisfy requirements for a Registration Data Access Protocol (RDAP).
   This draft also introduces an additional design consideration to
   define a simple use of HTTP.  Where complexity may reside, it is the
   goal of this specification 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 containing an HTTP URL 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 should return a 404 response.

   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

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   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), DNRD-AP.  This document and others
   from the IETF WEIRDS working group describe a single protocol, RDAP,
   for access to the data of both DNRs and Regional Internet Registries
   (RIRs).  RIRs are also often referred to as number resource
   registries and are responsible for the registration of IP address
   networks and autonomous system numbers.

3.  Design Intents

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

   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 a result 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, HTTP offers a number of transport protocol 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.

4.  Queries

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4.1.  Accept Header

   RDAP clients MUST include an Accept: header 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, or with
   no Accept: header.  One possibility would be to return a response in
   a media type suitable for rendering in a web browser.

4.2.  Query Parameters

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

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 SHOULD encode the answer in the format most appropriate according
   to the standard and defined rules for processing the HTTP Accept
   header, 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 SHOULD return either a 301 or a 307
   response code and an HTTP URL in the Location: header.  The client is
   expected to issue a subsequent 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.

   A server SHOULD use a 301 response to inform the client of a
   permanent move and a 307 response otherwise.  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

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   with another TLD operator (i.e.  a query for the domain bar in
   foo.example is found at http://foo.example/domain/bar).

   In other words, when generating the redirect url, the server will
   only alter the base of the URL.  It will not attempt to normalize or
   modify the path segment.

   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 SHOULD return a 404 response code.  Optionally, it MAY
   include additional information regarding the negative answer in the
   HTTP entity body.

5.4.  Malformed Queries

   If a server receives a query which it cannot understand, it SHOULD
   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 MAY 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 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.

5.6.  Cross-Origin Resource Sharing

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

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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 7).

   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 / "_" )

                                 Figure 1

   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 may 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.  IANA Considerations

7.1.  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 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.

   The following is a preliminary template for an RDAP extension

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      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

7.2.  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

8.  Internationalization Considerations

8.1.  URIs and IRIs

   Clients MAY use IRIs 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.

8.2.  Language Identifiers in Queries and Responses

   Depending on the data format of the response, servers MAY include
   data in character sets other than ASCII and languages other than
   English (the data format will most likely be in Unicode and almost
   certainly languages other than English will be encountered).  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 thus allowing clients to process and display the data

8.3.  Language Identifiers in HTTP Headers

   Given the description of the use of language identifiers in
   Section 8.2, unless otherwise specified servers SHOULD ignore the
   HTTP [RFC2616] Accept-Language header when formulating responses.

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

9.  Contributing Authors and Acknowledgements

   John Levine provided text to tighten up the Accept header 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.

10.  Normative 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.

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

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

              Kesteren, A., "Cross-Origin Resource Sharing", World Wide
              Web Consortium LastCall WD-cors-20130129, January 2013,

Appendix A.  Cache Busting

   To overcome issues with misbehaving HTTP [RFC2616] cache
   infrastructure, 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 B.  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 8.2 and Section 8.3.


      *  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

Authors' Addresses

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   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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