Using the Registration Data Access Protocol (RDAP) with HTTP
draft-ietf-weirds-using-http-03

Abstract

This document describes the usage of the Registration Data Access Protocol (RDAP) using 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 13, 2013.

Copyright Notice

Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved.

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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 192.0.2.0 might be http://example.com/ip/192.0.2.0.
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 format.
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 application.

2. Terminology

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].

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

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/rdap+json.

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 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 http://serv1.example.com/weirds/domain/example.com, the server redirecting to https://serv2.example.net/weirds2/ would set the Location: field to the value: https://serv2.example.net/weirds2/domain/example.com.

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 [W3C.WD-cors-20130129].

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 [RFC5234].

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

                

                    
  http://example.com/ip/192.0.2.0?__fuhgetaboutit=xyz123