Efficient RDAP Referrals
draft-brown-rdap-referrals-01
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Gavin Brown , Andy Newton | ||
| Last updated | 2024-11-20 | ||
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draft-brown-rdap-referrals-01
Registration Protocols Extensions (regext) G. Brown
Internet-Draft A. Newton
Intended status: Standards Track ICANN
Expires: 24 May 2025 20 November 2024
Efficient RDAP Referrals
draft-brown-rdap-referrals-01
Abstract
This document describes how RDAP servers can provide HTTP "Link"
header fields in RDAP responses to allow RDAP clients to efficiently
determine the URL of related RDAP records for a resource.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. RDAP Link Objects . . . . . . . . . . . . . . . . . . . . . . 3
3. HTTP "Link" Header Field . . . . . . . . . . . . . . . . . . 3
3.1. Registrar RDAP "Link" Header . . . . . . . . . . . . . . 4
4. RDAP Responses . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. RDAP HEAD requests . . . . . . . . . . . . . . . . . . . 4
5. RDAP Conformance . . . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Many Registration Data Access Protocol (RDAP, described in [RFC7480],
[RFC7481], [RFC9082], [RFC9083] and others) resources contain
referrals to related RDAP resources.
For example, in the domain space, an RDAP record for a domain name
received from the registry operator may include a referral to the
RDAP record for the same object provided by the sponsoring registrar,
while in the IP address space, an RDAP record for an address
allocation may include referrals to enclosing or sibling prefixes.
In both cases, RDAP service users are often equally if not more
interested in these related RDAP resources than the resource provided
by the TLD registry or RIR.
While RDAP supports redirection of RDAP requests using HTTP
redirections (which use a 3xx HTTP status and the "Location" header
field, see Section 15.4 of [RFC9110]), it is not possible for RDAP
servers to know _a priori_ whether a client requesting an RDAP record
is doing so because it wants to retrieve a related RDAP record, or
its own, so it can only respond by providing the full RDAP response.
The client must then parse that response in order to extract the
relevant URL from the "links" property of the object.
This results in the wasteful expenditure of time, compute resources
and bandwidth on the part of both the client and server.
This document describes how an RDAP server can use "Link" HTTP header
fields in responses to HEAD and GET requests to provide RDAP clients
with the URL of related RDAP records, without the need for a
signalling mechanism for the client to tell the server that it is
only interested in retrieving those URLs.
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2. RDAP Link Objects
RDAP link objects, described in Section 4.2 of [RFC9083], establish
unidirectional relationships between an RDAP resource and other web
resources, which may also be RDAP resources. The "rel" property
indicates the nature of the relationship, and its possible values are
described in [RFC8288].
If a link object has a "type" property which contains the value
"application/rdap+json", then clients can assume that the linked
resource is also an RDAP resource.
In the domain name space, this allows clients to discover the URL of
the sponsoring registrar's RDAP record for a given domain name, if
the "rel" property has the value "related", while in the IP address
space, the "up" and "down" values allow RDAP clients to navigate the
hierarchy of address space allocations.
3. HTTP "Link" Header Field
"Link" header fields, described in Section 3 of [RFC8288], provide a
means for describing a relationship between two resources, generally
between the requested resource and some other resource. The "Link"
header field is semantically equivalent to the <link> element in
HTML, and multiple "Link" headers may be present in the header of an
HTTP response.
"Link" header fields may contain most of the parameters that are also
present in Link objects in RDAP responses (See Section 4.2 of
[RFC9083]). So for example, an RDAP link object which has the
following JSON representation:
{
"value" : "https://example.com/context_uri",
"rel" : "self",
"href" : "https://example.com/target_uri",
"hreflang" : [ "en", "ch" ],
"title" : "title",
"media" : "screen",
"type" : "application/json"
}
may be represented in an HTTP response header as follows:
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Link: <https://example.com/target_uri>;
rel="self";
hreflang="en,ch";
title="title";
media="screen";
type="application/json"
In this example, the context URI is the URI that was requested by the
user agent.
3.1. Registrar RDAP "Link" Header
Following on from the above, the following RDAP link object, which
represents the RDAP URL of the sponsoring registrar of a resource:
{
"value": "https://rdap.example.com/domain/example.com",
"title": "URL of Sponsoring Registrar's RDAP Record",
"rel": "related",
"href": "https://rdap.example.com/domain/example.com",
"type": "application/rdap+json"
}
may be represented as follows:
Link: <https://rdap.example.com/domain/example.com>;
title="URL of Sponsoring Registrar's RDAP Record";
rel="related";
type="application/rdap+json"
4. RDAP Responses
In response to GET and HEAD RDAP requests, RDAP servers which
implement this specification MUST include a "Link" header field for
each link object which refers to an RDAP resource that is present in
the "links" array of the object in question. The server MAY also
include "Link" headers for link objects which refer to other types of
resource. In all cases, the link attributes MUST be the same in both
places.
4.1. RDAP HEAD requests
The HTTP HEAD method can be used for obtaining metadata about a
resource without transferring that resource (see Section 4.3.2 of
[RFC7231]).
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An RDAP client which only wishes to obtain the URLs of related RDAP
resources can issue a HEAD request for an RDAP resource and check the
response for the presence of an appropriate "Link" header field. If
the link is absent, it may then fall back to performing a GET
request.
An RDAP client interested in both the server's record and related
records can use the traditional method of performing a GET request
and extracting the link objects from the response. To improve
performance, RDAP clients MAY inspect the header of a response,
extract the link headers, and issue requests for the related record
in parallel while the request to the server is still in flight. As
an example, the cURL library provides the CURLOPT_HEADERFUNCTION
(https://curl.se/libcurl/c/CURLOPT_HEADERFUNCTION.html) configuration
option to provide a callback that is invoked as soon as it has
received header data.
5. RDAP Conformance
Servers which implement this specification MUST include the string
"link_headers" in the "rdapConformance" array in all RDAP responses.
6. IANA Considerations
IANA is requested to register the following value in the RDAP
Extensions Registry:
*Extension identifier:* link_headers
*Registry operator:* any.
*Published specification:* this document.
*Contact:* the authors of this document.
*Intended usage:* this extension indicates that the server will
provide links to related resources using "Link" headers in
responses to RDAP queries.
7. Normative References
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>.
[RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 7480, DOI 10.17487/RFC7480, March 2015,
<https://www.rfc-editor.org/info/rfc7480>.
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[RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 7481, DOI 10.17487/RFC7481, March 2015,
<https://www.rfc-editor.org/info/rfc7481>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/info/rfc8288>.
[RFC9082] Hollenbeck, S. and A. Newton, "Registration Data Access
Protocol (RDAP) Query Format", STD 95, RFC 9082,
DOI 10.17487/RFC9082, June 2021,
<https://www.rfc-editor.org/info/rfc9082>.
[RFC9083] Hollenbeck, S. and A. Newton, "JSON Responses for the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 9083, DOI 10.17487/RFC9083, June 2021,
<https://www.rfc-editor.org/info/rfc9083>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
Authors' Addresses
Gavin Brown
ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90292
United States of America
Email: gavin.brown@icann.org
URI: https://icann.org
Andy Newton
ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90292
United States of America
Email: andy.newton@icann.org
URI: https://icann.org
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