Registration Protocols Extensions M. Loffredo Internet-Draft M. Martinelli Intended status: Standards Track IIT-CNR/Registro.it Expires: November 28, 2019 May 27, 2019 Registration Data Access Protocol (RDAP) Partial Response draft-ietf-regext-rdap-partial-response-02 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 an 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 November 28, 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 Loffredo & Martinelli Expires November 28, 2019 [Page 1] Internet-Draft RDAP Partial Response May 2019 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. Negative Answers . . . . . . . . . . . . . . . . . . . . . . 8 7. RDAP Conformance . . . . . . . . . . . . . . . . . . . . . . 8 8. Implementation Status . . . . . . . . . . . . . . . . . . . . 8 8.1. IIT-CNR/Registro.it . . . . . . . . . . . . . . . . . . . 9 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 10. Security Considerations . . . . . . . . . . . . . . . . . . . 9 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 12.1. Normative References . . . . . . . . . . . . . . . . . . 10 12.2. 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 means 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) Loffredo & Martinelli Expires November 28, 2019 [Page 2] Internet-Draft RDAP Partial Response May 2019 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 contributes 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 data structure to avoid cases when the requested fields are invalid; o the request of some fields might not match the user access levels. Clients might put unauthorized fields in their requests and servers should define a strategy for providing a response: returning always an error response or returning a response that ignores the unauthorized fields. Loffredo & Martinelli Expires November 28, 2019 [Page 3] Internet-Draft RDAP Partial Response May 2019 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 (e.g. users interested in domains usually Loffredo & Martinelli Expires November 28, 2019 [Page 4] Internet-Draft RDAP Partial Response May 2019 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; Loffredo & Martinelli Expires November 28, 2019 [Page 5] Internet-Draft RDAP Partial Response May 2019 * "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" element 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 Loffredo & Martinelli Expires November 28, 2019 [Page 6] Internet-Draft RDAP Partial Response May 2019 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 included in "brief" and "full" field sets could be returned according to users access levels. Loffredo & Martinelli Expires November 28, 2019 [Page 7] Internet-Draft RDAP Partial Response May 2019 { "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. Negative Answers Each request including an unsupported field set SHOULD obtain an HTTP 400 (Bad Request) response code. Optionally, the response MAY include additional information regarding the negative answer in the HTTP entity body. 7. RDAP Conformance Servers returning the "subsetting_metadata" section in their responses MUST include "subsetting_level_0" in the rdapConformance array. 8. 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 Loffredo & Martinelli Expires November 28, 2019 [Page 8] Internet-Draft RDAP Partial Response May 2019 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. It is up to the individual working groups to use this information as they see fit". 8.1. 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 .it public test environment. 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 9. IANA Considerations IANA is requested to register the following value in the RDAP Extensions Registry: Extension identifier: subsetting Registry operator: Any Published specification: This document. Contact: IESG Intended usage: This extension describes a best practice for partial response provisioning. 10. 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 support RDAP operators to implement a versatile access control policy through the HTTP authentication Loffredo & Martinelli Expires November 28, 2019 [Page 9] Internet-Draft RDAP Partial Response May 2019 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. 11. Acknowledgements The authors would like to acknowledge Scott Hollenbeck for his contribution to this document. 12. References 12.1. 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, . [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, . [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, . [RFC7481] Hollenbeck, S. and N. Kong, "Security Services for the Registration Data Access Protocol (RDAP)", RFC 7481, DOI 10.17487/RFC7481, March 2015, . Loffredo & Martinelli Expires November 28, 2019 [Page 10] Internet-Draft RDAP Partial Response May 2019 [RFC7482] Newton, A. and S. Hollenbeck, "Registration Data Access Protocol (RDAP) Query Format", RFC 7482, DOI 10.17487/RFC7482, March 2015, . [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the Registration Data Access Protocol (RDAP)", RFC 7483, DOI 10.17487/RFC7483, March 2015, . [RFC8288] Nottingham, M., "Web Linking", RFC 8288, DOI 10.17487/RFC8288, October 2017, . 12.2. Informative References [CQL] Whitaker, G., "Catnap Query Language Reference", September 2017, . [FACEBOOK] facebook.com, "facebook for developers - Using the Graph API", July 2017, . [GOOGLE] google.com, "Making APIs Faster: Introducing Partial Response and Partial Update", March 2010, . [HATEOAS] Jedrzejewski, B., "HATEOAS - a simple explanation", 2018, . [LINKEDIN] linkedin.com, "Java One 2009: Building Consistent RESTful APIs in a High Performance Environment", July 2009, . [REST] Fielding, R., "Architectural Styles and the Design of Network-based Software Architectures", 2000, . Loffredo & Martinelli Expires November 28, 2019 [Page 11] Internet-Draft RDAP Partial Response May 2019 [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, . 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. 02: Added the "Negative Answers" section. Changed "IANA Considerations" section. 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 Loffredo & Martinelli Expires November 28, 2019 [Page 12]