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00 01
Registration Protocols Extensions M. Loffredo
Internet-Draft M. Martinelli
Intended status: Standards Track IIT-CNR/Registro.it
Expires: October 13, 2019 April 11, 2019
Registration Data Access Protocol (RDAP) Partial Response
draft-ietf-regext-rdap-partial-response-01
Abstract
The Registration Data Access Protocol (RDAP) does not include
capabilities to request partial responses. In fact, according to the
user authorization, the server can only return full responses.
Partial responses capability, especially in the case of search
queries, could bring benefits to both clients and servers. This
document describes a RDAP query extension that allows clients to
specify their preference for obtaining a partial response.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 13, 2019.
Copyright Notice
Copyright (c) 2019 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
(https://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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. Approaches to Partial Response Implementation . . . . . . . . 3
3. RDAP Path Segment Specification . . . . . . . . . . . . . . . 5
3.1. Subsetting Metadata . . . . . . . . . . . . . . . . . . . 5
3.1.1. Representing Subsetting Links . . . . . . . . . . . . 6
4. Dealing with Relationships . . . . . . . . . . . . . . . . . 7
5. Basic Field Sets . . . . . . . . . . . . . . . . . . . . . . 7
6. RDAP Conformance . . . . . . . . . . . . . . . . . . . . . . 8
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 8
7.1. IIT-CNR/Registro.it . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The use of partial response in RESTful API ([REST]) design is very
common. The rationale is quite simple: instead of returning objects
in API responses with all data fields, only a subset is returned.
The benefit is obvious: less data transferred over the network mean
less bandwidth usage, faster server response, less CPU time spent
both on the server and the client, as well as less memory usage on
the client.
Several leading APIs providers (e.g. LinkedIn [LINKEDIN], Facebook
[FACEBOOK], Google [GOOGLE]) implement the partial response feature
by providing an optional query parameter by which users require the
fields they wish to receive. Partial response is also considered a
leading principle by many best practices guidelines in REST APIs
implementation ([REST-API1], [REST-API2]) in order to improve
performance, save on bandwidth and possibly accelerate the overall
interaction. In other contexts, for example in digital libraries and
bibliographic catalogues, servers can provide responses according to
different element sets (i.e. "brief" to get back a short response and
"full" to get back the complete response)
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Currently, RDAP does not provide a client with any way to request a
partial response: the server can only provide the client with the
full response ([RFC7483]). Furthermore, servers cannot define the
limits of the results according to partial responses and this causes
strong inefficiencies.
The protocol described in this specification extends RDAP search
capabilities to enable partial responses, by adding a new query
parameter and using a RESTful web service. The service is
implemented using the Hypertext Transfer Protocol (HTTP) ([RFC7230])
and the conventions described in RFC 7480 ([RFC7480]).
1.1. 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 RFC 2119 ([RFC2119]).
2. Approaches to Partial Response Implementation
Looking at the implementation experiences described above, two
approaches to the implementation of partial response can be detected:
o the client declares explicitly the data fields to get back;
o the client declares a name identifying a server pre-defined set of
data fields.
The former is more flexible than the latter, because clients can
specify all the data fields they need. However, it has some
drawbacks:
o Fields have to be declared according to a given syntax. This is a
simple task when the data structure of the object is flat, but it
is much more difficult when the object has a tree structure like
the one of a JSON object. The presence of arrays and deep nested
objects contribute to complicate both the syntax definition of the
query and, consequently, the processing phase on the server side.
o Clients should perfectly know the returned object to avoid cases
when the required fields are not compliant with the object data
structure.
o The request of some fields cannot match the user access levels.
Clients could put unauthorized fields in their requests and
servers should define a strategy for providing a response: to
return always an error response or to return a response ignoring
the unauthorized fields.
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In addition to those listed above, RDAP responses raise some specific
issues:
o Most of the relevant information of the entity object is included
in the jCard but such information cannot be easily selected
because it is split into the items of a jagged array.
o RDAP responses contain some properties providing service
information (e.g. rdapConformance, links, notices, remarks, etc.)
which are not normally selected but they are just as important.
They could be returned anyway but, in this case, the server would
provide unrequested data.
As an example compliant to the first approach, the Catnap Query
Language ([CQL]) is a comprehensive expression language that can be
used to customize the JSON response of a RESTful web service. The
practical application of CQL to RDAP responses points out that
declaring explicitly the output fields would still be acceptable when
a few fields are requested but it would become very complicated if
the fields should be more. In the following, two CQL expressions for
a search domain query are shown (Figure 1): in the first, only
objectClassName and ldhName are requested, in the second, the fields
of a possible WHOIS-like response are listed.
https://example.com/rdap/domains?name=example*.com
&fields=domainSearchResults(objectClassName,ldhName)
https://example.com/rdap/domains?name=example*.com
&fields=domainSearchResults(objectClassName,ldhName,unicodeName,
status,
events(eventAction,eventDate),
entities(objectClassName,handle,roles),
nameservers(objectClassName,ldhName))
Figure 1: Examples of CQL expressions for a search domain query
The latter approach seems to facilitate RDAP interoperability. In
fact, servers can define some basic field sets which, if known to the
clients, can increase the probability to get a valid response. The
usage of field sets lets the query string be less complex. In
addition, the definition of pre-defined sets of fields makes easier
to establish the results limits.
Finally, considering that there is not a real need for RDAP users to
have the maximum flexibility in defining all the possible sets of
logically connected fields (for example, users interested in domains
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usually need to know the status, the creation date, the expire date
of each domain), the latter approach is preferred.
3. RDAP Path Segment Specification
The path segment defined in this section is an OPTIONAL extension of
search path segments defined in RFC 7482 ([RFC7482]). This document
defines an RDAP query parameter, "fieldSet", whose value is a string
identifying a server pre-defined set of fields (Figure 2).
https://example.com/rdap/domains?name=example*.com&fieldSet=afieldset
Figure 2: Example of RDAP search query reporting the "fieldSet"
parameter
3.1. Subsetting Metadata
According to most advanced principles in REST design, collectively
known as HATEOAS (Hypermedia as the Engine of Application State)
([HATEOAS]), a client entering a REST application through an initial
URI should use the server-provided links to dynamically discover
available actions and access the resources it needs. In this way,
the client is not requested to have prior knowledge of the service
and, consequently, to hard code the URIs of different resources.
This would allow the server to make URI changes as the API evolves
without breaking the clients. Definitively, a REST service should be
as self-descriptive as possible.
Therefore, servers implementing the query parameter described in this
specification SHOULD provide additional information in their
responses about the available field sets. Such information is
collected in a new data structure named "subsetting_metadata"
containing the following properties:
o "currentFieldSet": "String" (REQUIRED) either the value of
"fieldSet" parameter as specified in the query string or the field
set applied by default;
o "availableFieldSets": "AvailableFieldSet[]" (OPTIONAL) an array of
objects each one describing an alternate available field set.
Members are:
* "name": "String" (REQUIRED) the field set name;
* "default": "Boolean" (REQUIRED) whether the field set is
applied by default;
* "description": "String" (OPTIONAL) a human-readable description
of the field set;
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* "links": "Link[]" (OPTIONAL) an array of links as described in
RFC 8288 ([RFC8288]) containing the query string that applies
the field set.
3.1.1. Representing Subsetting Links
An RDAP server MAY use the "links" array of the "subsetting_metadata"
section to provide ready-made references ([RFC8288]) to the available
field sets (Figure 3). Each link represents a reference to an
alternate view of the results.
{
"rdapConformance": [
"rdap_level_0",
"subsetting_level_0"
],
...
"subsetting_metadata": {
"currentFieldSet": "afieldset",
"availableFieldSets": [
{
"name": "anotherfieldset",
"description": "Contains some fields",
"default": false,
"links": [
{
"value": "https://example.com/rdap/domains?name=*nr.com
&fieldSet=afieldset",
"rel": "alternate",
"href": "https://example.com/rdap/domains?name=*nr.com
&fieldSet=anotherfieldset",
"title": "Result Subset Link",
"type": "application/rdap+json"
},
...
]
},
"domainSearchResults": [
...
]
}
Figure 3: Example of a "subsetting_metadata" instance
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4. Dealing with Relationships
Some additional considerations can be made about how second level
objects could be represented within a field set. In fact, since the
topmost objects could be returned according to different field sets,
the same thing could go for their related objects. As a consequence,
the response could contain either no relationship or associated
objects which are in turn provided according to a field set.
5. Basic Field Sets
In order to improve interoperability between clients and servers, the
name, as well as the list of fields for each field set, should be
shared by most of RDAP providers. This section defines three basic
field sets which servers MAY implement to facilitate their
interaction with clients:
o "id": the server provides only the key field ("handle" for
entities, "ldhName" for domains and nameservers). This field set
could be used when the client wants to simply obtain a collection
of object identifiers (Figure 4);
o "brief": it contains the fields that can be included in a "short"
response. This field set could be used when the client is asking
for a subset of the full response which gives a basic knowledge of
each object;
o "full": it contains all the information the server can provide for
a particular object.
The "objectClassName" field is implicitly included in each of the
above field sets. RDAP providers MAY add any property providing
service information.
Fields belonging to "brief" and "full" field sets could be returned
according to users access levels.
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{
"rdapConformance": [
"rdap_level_0",
],
...
"domainSearchResults": [
{
"objectClassName": "domain",
"ldhName": "example1.com"
},
{
"objectClassName": "domain",
"ldhName": "example2.com"
},
...
]
}
Figure 4: Example of RDAP response according to the "id" field set
6. RDAP Conformance
Servers returning the "subsetting_metadata" section in their
responses MUST include "subsetting_level_0" in the rdapConformance
array.
7. Implementation Status
NOTE: Please remove this section and the reference to RFC 7942 prior
to publication as an RFC.
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in RFC 7942
([RFC7942]). The description of implementations in this section is
intended to assist the IETF in its decision processes in progressing
drafts to RFCs. Please note that the listing of any individual
implementation here does not imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information
presented here that was supplied by IETF contributors. This is not
intended as, and must not be construed to be, a catalog of available
implementations or their features. Readers are advised to note that
other implementations may exist.
According to RFC 7942, "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
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It is up to the individual working groups to use this information as
they see fit".
7.1. IIT-CNR/Registro.it
Responsible Organization: Institute of Informatics and Telematics
of National Research Council (IIT-CNR)/Registro.it
Location: https://rdap.pubtest.nic.it/
Description: This implementation includes support for RDAP queries
using data from the public test environment of .it ccTLD.
Level of Maturity: This is a "proof of concept" research
implementation.
Coverage: This implementation includes all of the features
described in this specification.
Contact Information: Mario Loffredo, mario.loffredo@iit.cnr.it
8. Security Considerations
Search query typically requires more server resources (such as
memory, CPU cycles, and network bandwidth) when compared to lookup
query. This increases the risk of server resource exhaustion and
subsequent denial of service due to abuse. Partial response can
contribute together with other strategies (e.g. restricting search
functionality, limiting the rate of search requests, truncating and
paging results) to mitigate this risk.
Furthermore, partial response can help RDAP operators to regulate
access control based on client identification, implemented by HTTP
authentication mechanisms as described in RFC 7481 ([RFC7481]). In
fact, RDAP operators can follow different, not alternative,
approaches to the building of responses according to the user access
levels:
o the list of fields for each set can be different according to the
user access levels;
o some field sets could be available only to some users.
Servers can also define different results limits according to the
available field sets, so a more flexible truncation strategy can be
realized.
Therefore, the new query parameter presented in this document
provides the RDAP operators with a way to implement a secure server
without penalizing its efficiency.
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9. IANA Considerations
This document has no actions for IANA.
10. Acknowledgements
The authors would like to acknowledge Scott Hollenbeck for his
contribution to this document.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC7480] Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
Registration Data Access Protocol (RDAP)", RFC 7480,
DOI 10.17487/RFC7480, March 2015,
<https://www.rfc-editor.org/info/rfc7480>.
[RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the
Registration Data Access Protocol (RDAP)", RFC 7481,
DOI 10.17487/RFC7481, March 2015,
<https://www.rfc-editor.org/info/rfc7481>.
[RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access
Protocol (RDAP) Query Format", RFC 7482,
DOI 10.17487/RFC7482, March 2015,
<https://www.rfc-editor.org/info/rfc7482>.
[RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the
Registration Data Access Protocol (RDAP)", RFC 7483,
DOI 10.17487/RFC7483, March 2015,
<https://www.rfc-editor.org/info/rfc7483>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/info/rfc8288>.
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11.2. Informative References
[CQL] Whitaker, G., "Catnap Query Language Reference", September
2017, <https://github.com/gregwhitaker/catnap/wiki/
Catnap-Query-Language-Reference>.
[FACEBOOK]
facebook.com, "facebook for developers - Using the Graph
API", July 2017, <https://developers.facebook.com/docs/
graph-api/using-graph-api>.
[GOOGLE] google.com, "Making APIs Faster: Introducing Partial
Response and Partial Update", March 2010,
<http://googlecode.blogspot.it/2010/03/
making-apis-faster-introducing-partial.html>.
[HATEOAS] Jedrzejewski, B., "HATEOAS - a simple explanation", 2018,
<https://www.e4developer.com/2018/02/16/
hateoas-simple-explanation/>.
[LINKEDIN]
linkedin.com, "Java One 2009: Building Consistent RESTful
APIs in a High Performance Environment", July 2009,
<https://blog.linkedin.com/2009/07/08/brandon-duncan-java-
one-building-consistent-restful-apis-in-a-high-
performance-environment>.
[REST] Fielding, R., "Architectural Styles and the Design of
Network-based Software Architectures", 2000,
<http://www.restapitutorial.com/media/
RESTful_Best_Practices-v1_1.pdf>.
[REST-API1]
Jobinesh, P., "RESTful Java Web Services - Second
Edition", September 2015.
[REST-API2]
Masse, M., "REST API Design Rulebook", October 2011.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
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Appendix A. Change Log
00: Initial working group version ported from draft-loffredo-regext-
rdap-partial-response-03
01: Removed "FOR DISCUSSION" items. Changed the basic field sets
from REQUIRED to OPTIONAL. Removed the definition of fields
included in "brief" field set. Provided a more detailed
description of "subsetting_metadata" structure. Removed some
references.
Authors' Addresses
Mario Loffredo
IIT-CNR/Registro.it
Via Moruzzi,1
Pisa 56124
IT
Email: mario.loffredo@iit.cnr.it
URI: http://www.iit.cnr.it
Maurizio Martinelli
IIT-CNR/Registro.it
Via Moruzzi,1
Pisa 56124
IT
Email: maurizio.martinelli@iit.cnr.it
URI: http://www.iit.cnr.it
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