[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]
Versions: (draft-loffredo-regext-rdap-sorting-and-paging)
00 01 02 03 04 05 06
Registration Protocols Extensions M. Loffredo
Internet-Draft M. Martinelli
Intended status: Standards Track IIT-CNR/Registro.it
Expires: November 28, 2019 S. Hollenbeck
Verisign Labs
May 27, 2019
Registration Data Access Protocol (RDAP) Query Parameters for Result
Sorting and Paging
draft-ietf-regext-rdap-sorting-and-paging-02
Abstract
The Registration Data Access Protocol (RDAP) does not include core
functionality for clients to provide sorting and paging parameters
for control of large result sets. This omission can lead to
unpredictable server processing of queries and client processing of
responses. This unpredictability can be greatly reduced if clients
can provide servers with their preferences for managing large
responses. This document describes RDAP query extensions that allow
clients to specify their preferences for sorting and paging result
sets.
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
Loffredo, et al. Expires November 28, 2019 [Page 1]
Internet-Draft RDAP Sorting and Paging May 2019
(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
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 . . . . . . . . . . . . 4
2. RDAP Query Parameter Specification . . . . . . . . . . . . . 4
2.1. Sorting and Paging Metadata . . . . . . . . . . . . . . . 4
2.2. "count" Parameter . . . . . . . . . . . . . . . . . . . . 6
2.3. "sort" Parameter . . . . . . . . . . . . . . . . . . . . 7
2.3.1. Sorting Properties Declaration . . . . . . . . . . . 7
2.3.2. Representing Sorting Links . . . . . . . . . . . . . 11
2.4. "cursor" Parameter . . . . . . . . . . . . . . . . . . . 12
2.4.1. Representing Paging Links . . . . . . . . . . . . . . 15
3. Negative Answers . . . . . . . . . . . . . . . . . . . . . . 16
4. RDAP Conformance . . . . . . . . . . . . . . . . . . . . . . 17
5. Implementation Considerations . . . . . . . . . . . . . . . . 17
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 17
6.1. IIT-CNR/Registro.it . . . . . . . . . . . . . . . . . . . 18
6.2. Google Registry . . . . . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 21
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction
The availability of functionality for result sorting and paging
provides benefits to both clients and servers in the implementation
of RESTful services [REST]. These benefits include:
o reducing the server response bandwidth requirements;
o improving server response time;
o improving query precision and, consequently, obtaining more
reliable results;
o decreasing server query processing load;
o reducing client response processing time.
Loffredo, et al. Expires November 28, 2019 [Page 2]
Internet-Draft RDAP Sorting and Paging May 2019
Approaches to implementing features for result sorting and paging can
be grouped into two main categories:
1. Sorting and paging are implemented through the introduction of
additional parameters in the query string (i.e. ODATA protocol
[OData-Part1]);
2. Information related to the number of results and the specific
portion of the result set to be returned, in addition to a set of
ready-made links for the result set scrolling, are inserted in
the HTTP header of the request/response.
However, there are some drawbacks associated with use of the HTTP
header. First, the header properties cannot be set directly from a
web browser. Moreover, in an HTTP session, the information on the
status (i.e. the session identifier) is usually inserted in the
header or in the cookies, while the information on the resource
identification or the search type is included in the query string.
The second approach is therefore not compliant with the HTTP standard
[RFC7230]. As a result, this document describes a specification
based on use of query parameters.
Currently the RDAP protocol [RFC7482] defines two query types:
o lookup: the server returns only one object;
o search: the server returns a collection of objects.
While the lookup query does not raise issues in the response
management, the search query can potentially generate a large result
set that could be truncated according to the server limits. In
addition, it is not possible to obtain the total number of the
objects found that might be returned in a search query response
[RFC7483]. Lastly, there is no way to specify sort criteria to
return the most relevant objects at the beginning of the result set.
Therefore, the client might traverse the whole result set to find the
relevant objects or, due to truncation, could not find them at all.
The specification described in this document extends RDAP query
capabilities to enable result sorting and paging, by adding new query
parameters that can be applied to RDAP search path segments. The
service is implemented using the Hypertext Transfer Protocol (HTTP)
[RFC7230] and the conventions described in RFC 7480 [RFC7480].
The implementation of the new parameters is technically feasible, as
operators for counting, sorting and paging rows are currently
supported by the major RDBMSs.
Loffredo, et al. Expires November 28, 2019 [Page 3]
Internet-Draft RDAP Sorting and Paging May 2019
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 [RFC2119].
2. RDAP Query Parameter Specification
The new query parameters are OPTIONAL extensions of path segments
defined in RFC 7482 [RFC7482]. They are as follows:
o "count": a boolean value that allows a client to request the total
number of objects found (that due to truncation can be different
from the number of returned objects);
o "sort": a string value that allows a client to request a specific
sort order for the result set;
o "cursor": a string value representing a pointer to a specific
fixed size portion of the result set.
Augmented Backus-Naur Form (ABNF) [RFC5234] is used in the following
sections to describe the formal syntax of these new parameters.
2.1. Sorting and Paging 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 parameters described in
this specification SHOULD provide additional information in their
responses about both the available sorting criteria and the possible
pagination. Such information is collected in two new data structures
named, respectively, "sorting_metadata" and "paging_metadata".
Obviously, both the new data structures are OPTIONAL because their
presence in the response not only depends on the implementation of
sorting and paging query capabilities but also on some situations
related to the results. For example, it is quite natural to expect
Loffredo, et al. Expires November 28, 2019 [Page 4]
Internet-Draft RDAP Sorting and Paging May 2019
that the "paging_metadata" element will not be present at the last
result page when the server implements only the forward pagination.
The "sorting_metadata" structure contains the following properties:
o "currentSort": "String" (OPTIONAL) either the value of sort
"parameter" as specified in the query string or the sort applied
by default, if any;
o "availableSorts": "AvailableSort[]" (OPTIONAL) an array of objects
each one describing an alternate available sorting criterion.
Members are:
* "property": "String" (REQUIRED) the name that can be used by
the client to request the sorting criterion;
* "default": "Boolean" (REQUIRED) whether the sorting criterion
is applied by default;
* "jsonPath": "String" (OPTIONAL) the JSON Path of the RDAP field
corresponding to the property;
* "links": "Link[]" (OPTIONAL) an array of links as described in
RFC 8288 [RFC8288] containing the query string that applies the
sorting criterion.
At least one between "currentSort" and "availableSorts" MUST be
present.
The "paging_metadata" structure contains the following fields:
o "totalCount": "Numeric" (OPTIONAL) a numeric value representing
the total number of objects found. It is provided if the query
string contains the "count" parameter;
o "pageCount": "Numeric" (OPTIONAL) a numeric value representing the
number of objects returned in the current page. It is provided
when the total number of objects exceeds the page size. This
property is redundant for clients because the page size can be
derived from the length of the search results array but it can be
helpful if the end user interacts with the server through a web
browser;
o "links": "Link[]" (OPTIONAL) an array of links as described in RFC
8288 [RFC8288] containing the reference to next page. In this
specification, only the forward pagination is dealt because it is
considered satisfactory in order to traverse the result set.
Examples of additional references are to: the previous page, the
first page, the last page.
At least one between "totalCount" and "links" MUST be present.
Loffredo, et al. Expires November 28, 2019 [Page 5]
Internet-Draft RDAP Sorting and Paging May 2019
2.2. "count" Parameter
Currently the RDAP protocol does not allow a client to determine the
total number of the results in a query response when the result set
is truncated. This is rather inefficient because the user cannot
evaluate the query precision and, at the same time, cannot receive
information that could be relevant.
The "count" parameter provides additional functionality (Figure 1)
that allows a client to request information from the server that
specifies the total number of elements matching the search pattern.
https://example.com/rdap/domains?name=*nr.com&count=true
Figure 1: Example of RDAP query reporting the "count" parameter
The ABNF syntax is the following:
count = "count=" ( trueValue / falseValue )
trueValue = ("true" / "yes" / "1")
falseValue = ("false" / "no" / "0")
A trueValue means that the server MUST provide the total number of
the objects in the "totalCount" field of the "paging_metadata"
element (Figure 2). A falseValue means that the server MUST NOT
provide this number.
{
"rdapConformance": [
"rdap_level_0",
"paging_level_0"
],
...
"paging_metadata": {
"totalCount": 73
},
"domainSearchResults": [
...
]
}
Figure 2: Example of RDAP response with "paging_metadata" element
containing the "totalCount" field
Loffredo, et al. Expires November 28, 2019 [Page 6]
Internet-Draft RDAP Sorting and Paging May 2019
2.3. "sort" Parameter
The RDAP protocol does not provide any capability to specify results
sort criteria. A server could implement a default sorting scheme
according to the object class, but this feature is not mandatory and
might not meet user requirements. Sorting can be addressed by the
client, but this solution is rather inefficient. Sorting features
provided by the RDAP server could help avoid truncation of relevant
results.
The "sort" parameter allows the client to ask the server to sort the
results according to the values of one or more properties and
according to the sort direction of each property. The ABNF syntax is
the following:
sort = "sort=" sortItem *( "," sortItem )
sortItem = property-ref [":" ( "a" / "d" ) ]
property-ref = ALPHA *( ALPHA / DIGIT / "_" )
"a" means that the ascending sort MUST be applied, "d" means that the
descending sort MUST be applied. If the sort direction is absent, an
ascending sort MUST be applied (Figure 3).
https://example.com/rdap/domains?name=*nr.com&sort=ldhName
https://example.com/rdap/domains?name=*nr.com&sort=registrationDate:d
https://example.com/rdap/domains?name=*nr.com&sort=lockedDate,ldhName
Figure 3: Examples of RDAP query reporting the "sort" parameter
If the "sort" parameter reports an allowed sorting property, it MUST
be provided in the "currentSort" field of the "sorting_metadata"
element.
2.3.1. Sorting Properties Declaration
In the "sort" parameter ABNF syntax, property-ref represents a
reference to a property of an RDAP object. Such a reference could be
expressed by using a JSON Path. The JSON Path in a JSON document
[RFC8259] is equivalent to the XPath [W3C.CR-xpath-31-20161213] in a
XML document. For example, the JSON Path to select the value of the
ASCII name inside an RDAP domain object is "$.ldhName", where $
identifies the root of the document (DOM). Another way to select a
value inside a JSON document is the JSON Pointer [RFC6901]. While
JSON Path or JSON Pointer are both standard ways to select any value
inside JSON data, neither is particularly easy to use (e.g.
Loffredo, et al. Expires November 28, 2019 [Page 7]
Internet-Draft RDAP Sorting and Paging May 2019
"$.events[?(@.eventAction='registration')].eventDate" is the JSON
Path expression of the registration date in an RDAP domain object).
Therefore, this specification provides a definition of property-ref
in terms of RDAP properties. However, not all the RDAP properties
are suitable to be used in sort criteria, such as:
o properties providing service information (e.g. links, notices,
remarks, etc.);
o multivalued properties (e.g. status, roles, variants, etc.);
o properties modeling relationships to other objects (e.g.
entities).
On the contrary, some properties expressed as values of other
properties (e.g. registration date) could be used in such a context.
In the following, a list of properties an RDAP server MAY implement
is presented. The properties are divided in two groups: object
common properties and object specific properties.
o Object common properties. Object common properties are derived
from the merge of the "eventAction" and the "eventDate"
properties. The following values of the "sort" parameter are
defined:
* registrationDate
* reregistrationDate
* lastChangedDate
* expirationDate
* deletionDate
* reinstantiationDate
* transferDate
* lockedDate
* unlockedDate
o Object specific properties. With regard to the specific
properties, some of them are already defined among the query
paths. In the following a list of possible sorting properties,
grouped by objects, is shown:
* Domain: ldhName
* Nameserver: ldhName, ipV4, ipV6.
* Entity: fn, handle, org, email, voice, country, city.
The correspondence between the sorting properties and the RDAP fields
is shown in Table 1:
Loffredo, et al. Expires November 28, 2019 [Page 8]
Internet-Draft RDAP Sorting and Paging May 2019
+------------+------------+---------------+------------+------------+
| Object | Sorting | RDAP property | Reference | Reference |
| class | property | | in RFC | in RFC |
| | | | 7483 | 6350 |
+------------+------------+---------------+------------+------------+
| Searchable | Common | eventAction | 4.5. | |
| objects | properties | values | | |
| | | suffixed by | | |
| | | "Date" | | |
| | | | | |
| Domain | ldhName | ldhName | 5.3. | |
| | | | | |
| Nameserver | ldhName | ldhName | 5.2. | |
| | ipV4 | v4 ipAddress | 5.2. | |
| | ipV6 | v6 ipAddress | 5.2. | |
| | | | | |
| Entity | handle | handle | 5.1. | |
| | fn | vcard fn | 5.1. | 6.2.1 |
| | org | vcard org | 5.1. | 6.6.4 |
| | voice | vcard tel | 5.1. | 6.4.1 |
| | | with | | |
| | | type="voice" | | |
| | email | vcard email | 5.1. | 6.4.2 |
| | country | country name | 5.1. | 6.3.1 |
| | | in vcard adr | | |
| | city | locality in | 5.1. | 6.3.1 |
| | | vcard adr | | |
+------------+------------+---------------+------------+------------+
Table 1: Sorting properties definition
With regard to the definitions in Table 1, some further
considerations must be made to disambiguate cases where the RDAP
property is multivalued:
o even if a nameserver can have multiple IPv4 and IPv6 addresses,
the most common configuration includes one address for each IP
version. Therefore, the assumption of having a single IPv4 and/or
IPv6 value for a nameserver cannot be considered too stringent;
o with the exception of handle values, all the sorting properties
defined for entity objects can be multivalued according to the
definition of vCard as given in RFC6350 [RFC6350]. When more than
a value is reported, sorting can be applied to the preferred value
identified by the parameter pref="1".
Each RDAP provider MAY define other sorting properties than those
shown in this document.
Loffredo, et al. Expires November 28, 2019 [Page 9]
Internet-Draft RDAP Sorting and Paging May 2019
The "jsonPath" field in the "sorting_metadata" element is used to
clarify the RDAP field the sorting property refers to. The mapping
between the sorting properties and the JSON Paths of the RDAP fields
is shown in Table 2. The JSON Paths are provided according to the
Goessner v.0.8.0 specification ([GOESSNER-JSON-PATH]):
+-------+-------------+---------------------------------------------+
| Objec | Sorting | JSON Path |
| t | property | |
| class | | |
+-------+-------------+---------------------------------------------+
| Searc | registratio | "$.domainSearchResults[*].events[?(@.eventA |
| hable | nDate | ction=="registration")].eventDate |
| objec | | |
| ts | | |
| | reregistrat | "$.domainSearchResults[*].events[?(@.eventA |
| | ionDate | ction=="reregistration")].eventDate |
| | lastChanged | "$.domainSearchResults[*].events[?(@.eventA |
| | Date | ction=="lastChanged")].eventDate |
| | expirationD | "$.domainSearchResults[*].events[?(@.eventA |
| | ate | ction=="expiration")].eventDate |
| | deletionDat | "$.domainSearchResults[*].events[?(@.eventA |
| | e | ction=="deletion")].eventDate |
| | reinstantia | "$.domainSearchResults[*].events[?(@.eventA |
| | tionDate | ction=="reinstantiation")].eventDate |
| | transferDat | "$.domainSearchResults[*].events[?(@.eventA |
| | e | ction=="transfer")].eventDate |
| | lockedDate | "$.domainSearchResults[*].events[?(@.eventA |
| | | ction=="locked")].eventDate |
| | unlockedDat | "$.domainSearchResults[*].events[?(@.eventA |
| | e | ction=="unlocked")].eventDate |
| | | |
| Domai | ldhName | $.domainSearchResults[*].ldhName |
| n | | |
| | | |
| Names | ldhName | $.nameserverSearchResults[*].ldhName |
| erver | | |
| | ipV4 | $.nameserverSearchResults[*].ipAddresses.v4 |
| | | [0] |
| | ipV6 | $.nameserverSearchResults[*].ipAddresses.v6 |
| | | [0] |
| | | |
| Entit | handle | $.entitySearchResults[*].handle |
| y | | |
| | fn | $.entitySearchResults[*].vcardArray[1][?(@[ |
| | | 0]="fn")][3] |
| | org | $.entitySearchResults[*].vcardArray[1][?(@[ |
| | | 0]="org")][3] |
Loffredo, et al. Expires November 28, 2019 [Page 10]
Internet-Draft RDAP Sorting and Paging May 2019
| | voice | $.entitySearchResults[*].vcardArray[1][?(@[ |
| | | 0]=="tel" && @[1].type=="voice")][3] |
| | email | $.entitySearchResults[*].vcardArray[1][?(@[ |
| | | 0]=="email")][3] |
| | country | $.entitySearchResults[*].vcardArray[1][?(@[ |
| | | 0]=="adr")][3][6] |
| | city | $.entitySearchResults[*].vcardArray[1][?(@[ |
| | | 0]=="adr")][3][3] |
+-------+-------------+---------------------------------------------+
Table 2: Sorting properties - JSON Path Mapping
2.3.2. Representing Sorting Links
An RDAP server MAY use the "links" array of the "sorting_metadata"
element to provide ready-made references [RFC8288] to the available
sort criteria (Figure 4). Each link represents a reference to an
alternate view of the results.
Loffredo, et al. Expires November 28, 2019 [Page 11]
Internet-Draft RDAP Sorting and Paging May 2019
{
"rdapConformance": [
"rdap_level_0",
"sorting_level_0"
],
...
"sorting_metadata": {
"currentSort": "ldhName",
"availableSorts": [
{
"property": "registrationDate",
"jsonPath": "$.domainSearchResults[*]
.events[?(@.eventAction==\"registration\")].eventDate",
"default": false,
"links": [
{
"value": "https://example.com/rdap/domains?name=*nr.com
&sort=ldhName",
"rel": "alternate",
"href": "https://example.com/rdap/domains?name=*nr.com
&sort=registrationDate",
"title": "Result Ascending Sort Link",
"type": "application/rdap+json"
},
{
"value": "https://example.com/rdap/domains?name=*nr.com
&sort=ldhName",
"rel": "alternate",
"href": "https://example.com/rdap/domains?name=*nr.com
&sort=registrationDate:d",
"title": "Result Descending Sort Link",
"type": "application/rdap+json"
}
]
},
"domainSearchResults": [
...
]
}
Figure 4: Example of a "sorting_metadata" instance to implement
result sorting
2.4. "cursor" Parameter
An RDAP query could return a response with hundreds, even thousands,
of objects, especially when partial matching is used. For that
Loffredo, et al. Expires November 28, 2019 [Page 12]
Internet-Draft RDAP Sorting and Paging May 2019
reason, the cursor parameter addressing result pagination is defined
to make responses easier to handle.
Using limit and offset operators represents the most common way to
implement results pagination. Both of them can be used individually:
o "limit": means that the server must return the first N objects of
the result set;
o "offset": means that the server must skip the first N objects and
must return objects starting from position N+1.
When limit and offset are used together, they allow to identify a
specific portion of the result set. For example, the pair
"offset=100,limit=50" returns first 50 objects starting from position
101 of the result set.
However, offset pagination raises some well known drawbacks:
o when offset has a very high value, scrolling the result set could
take some time;
o it always requires to fetch all the rows before dropping as many
rows as specified by offset;
o it may return inconsistent pages when data are frequently updated
(i.e. real-time data) but this doesn't seem the case of
registration data.
An alternative approach to offset pagination is keyset pagination
[SEEK] which consists in adding a query condition that enables the
seletion of the only data not yet returned. This method has been
taken as the basis for the implementation of a "cursor" parameter
[CURSOR] by some REST API providers (e.g.
[CURSOR-API1],[CURSOR-API2]). The cursor is an opaque URL-safe
string representing a logical pointer to the first result of the next
page (Figure 5). Basically, the cursor is the encryption of the key
value identifying the last row of the current page. For example, the
cursor value "a2V5PXRoZWxhc3Rkb21haW5vZnRoZXBhZ2UuY29t=" is the mere
Base64 encoding of "key=thelastdomainofthepage.com".
The ABNF syntax is the following:
cursor = "cursor=" ( ALPHA / DIGIT / "/" / "=" / "-" / "_" )
Loffredo, et al. Expires November 28, 2019 [Page 13]
Internet-Draft RDAP Sorting and Paging May 2019
https://example.com/rdap/domains?name=*nr.com
&cursor=wJlCDLIl6KTWypN7T6vc6nWEmEYe99Hjf1XY1xmqV-M=
Figure 5: An example of RDAP query reporting the "cursor" parameter
Nevertheless, even cursor pagination can be troublesome:
o it needs at least one key field;
o it does not allow to sort just by any field because the sorting
criterion must contain a key;
o it works best with full composite values support by DBMS (i.e.
[x,y]>[a,b]), emulation is possible but ugly and less performant;
o it does not allow to directly navigate to arbitrary pages because
the result set must be scrolled in sequential order starting from
the initial page;
o implementing the bi-directional navigation is tedious because all
comparison and sort operations have to be reversed.
Furthermore, in the RDAP context, some additional considerations can
be made:
o an RDAP object is a conceptual aggregation of information
generally collected from more than one data structure (e.g. table)
and this makes even harder for the developers the implementation
of the keyset pagination that is already quite difficult. For
example, the entity object can gather information from different
data structures (registrars, registrants, contacts, resellers, and
so on), each one with its own key field mapping the RDAP entity
handle;
o depending on the number of the page results as well as the number
and the complexity of the properties of each RDAP object in the
response, the time required by offset pagination to skip the
previous pages could be much faster than the processing time
needed to build the current page. In fact, RDAP objects are
usually formed by information belonging to multiple data
structures and containing multivalued properties (i.e. arrays)
and, therefore, data selection might be a time consuming process.
This situation occurs even though the selection is supported by
indexes;
o depending on the access levels defined by each RDAP operator, the
increase of complexity and the decrease of flexibility of cursor
Loffredo, et al. Expires November 28, 2019 [Page 14]
Internet-Draft RDAP Sorting and Paging May 2019
pagination with respect to the offset pagination could be
considered impractical.
Ultimately, both pagination methods have benefits and drawbacks.
That said, the cursor parameter can be used not only to encode the
key value but also the information about offset pagination. For
example, the cursor value "b2Zmc2V0PTEwMCxsaW1pdD01MAo=" is the mere
Base64 encoding of "offset=100,limit=50". This solution lets RDAP
providers to implement a pagination method according to their needs,
the user access levels, the submitted queries. In addition, servers
can change the method over time without announcing anything to the
clients.
2.4.1. Representing Paging Links
An RDAP server SHOULD use the "links" array of the "paging_metadata"
element to provide a ready-made reference [RFC8288] to the next page
of the result set (Figure 6). Examples of additional "rel" values a
server MAY implements are "first", "last", "prev".
Loffredo, et al. Expires November 28, 2019 [Page 15]
Internet-Draft RDAP Sorting and Paging May 2019
{
"rdapConformance": [
"rdap_level_0",
"paging_level_0"
],
...
"notices": [
{
"title": "Search query limits",
"type": "result set truncated due to excessive load",
"description": [
"search results for domains are limited to 10"
]
}
],
"paging_metadata": {
"totalCount": 73,
"pageCount": 10,
"links": [
{
"value": "https://example.com/rdap/domains?name=*nr.com",
"rel": "next",
"href": "https://example.com/rdap/domains?name=*nr.com
&cursor=wJlCDLIl6KTWypN7T6vc6nWEmEYe99Hjf1XY1xmqV-M=",
"title": "Result Pagination Link",
"type": "application/rdap+json"
}
]
},
"domainSearchResults": [
...
]
}
Figure 6: Example of a "paging_metadata" instance to implement cursor
pagination
3. Negative Answers
The value constraints for the parameters are defined by their ABNF
syntax. Therefore, each request including an invalid value for a
parameter SHOULD obtain an HTTP 400 (Bad Request) response code. The
same response SHOULD be returned in the following cases:
o if the client provides an unsupported value for the "sort"
parameter in both single and multi sort;
o if the client submits an invalid value for the "cursor" parameter.
Loffredo, et al. Expires November 28, 2019 [Page 16]
Internet-Draft RDAP Sorting and Paging May 2019
Optionally, the response MAY include additional information regarding
the negative answer in the HTTP entity body.
4. RDAP Conformance
Servers returning the "paging_metadata" element in their response
MUST include "paging_level_0" in the rdapConformance array as well as
servers returning the "sorting_metadata" element MUST include
"sorting_level_0".
5. Implementation Considerations
The implementation of the new parameters is technically feasible, as
operators for counting, sorting and paging are currently supported by
the major RDBMSs.
Similar operators are completely or partially supported by the most
known NoSQL databases (MongoDB, CouchDB, HBase, Cassandra, Hadoop) so
the implementation of the new parameters seems to be practicable by
servers working without the use of an RDBMS.
Furthermore, both two pagination methods don't require the server to
handle the result set in a storage area across the requests since a
new result set is generated each time a request is submitted.
6. 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.
Loffredo, et al. Expires November 28, 2019 [Page 17]
Internet-Draft RDAP Sorting and Paging May 2019
It is up to the individual working groups to use this information as
they see fit".
6.1. 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
6.2. Google Registry
Responsible Organization: Google Registry
Location: https://www.registry.google/rdap/
Description: This implementation includes support for RDAP queries
for TLDs such as .google, .how, .soy, and .xn--q9jyb4c . The RDAP
server implements cursor pagination. The link used to request the
next page is included in the notice section of the response.
Level of Maturity: Production.
Coverage: This implementation includes the "cursor" parameter
described in this specification.
Contact Information: Brian Mountford, mountford@google.com
7. IANA Considerations
IANA is requested to register the following values in the RDAP
Extensions Registry:
Extension identifier: paging
Registry operator: Any
Published specification: This document.
Contact: IESG <iesg@ietf.org>
Intended usage: This extension describes a best practice for
result set paging.
Extension identifier: sorting
Registry operator: Any
Published specification: This document.
Contact: IESG <iesg@ietf.org>
Intended usage: This extension describes a best practice for
result set sorting.
Loffredo, et al. Expires November 28, 2019 [Page 18]
Internet-Draft RDAP Sorting and Paging May 2019
8. Security Considerations
Security services for the operations specified in this document are
described in RFC 7481 [RFC7481].
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. This risk can be
mitigated by either restricting search functionality and limiting the
rate of search requests. Servers can also reduce their load by
truncating the results in the response. However, this last security
policy can result in a higher inefficiency if the RDAP server does
not provide any functionality to return the truncated results.
The new parameters presented in this document provide the RDAP
operators with a way to implement a secure server without penalizing
its efficiency. The "count" parameter gives the user a measure to
evaluate the query precision and, at the same time, returns a
significant information. The "sort" parameter allows the user to
obtain the most relevant information at the beginning of the result
set. In both cases, the user doesn't need to submit further
unnecessary search requests. Finally, the "cursor" parameter enables
the user to scroll the result set by submitting a sequence of
sustainable queries according to the server limits.
9. Acknowledgements
The authors would like to acknowledge Brian Mountford for his
contribution to the development of this document.
10. References
10.1. Normative References
[ISO.3166.1988]
International Organization for Standardization, "Codes for
the representation of names of countries, 3rd edition",
ISO Standard 3166, August 1988.
[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>.
Loffredo, et al. Expires November 28, 2019 [Page 19]
Internet-Draft RDAP Sorting and Paging May 2019
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC6350] Perreault, S., "vCard Format Specification", RFC 6350,
DOI 10.17487/RFC6350, August 2011,
<https://www.rfc-editor.org/info/rfc6350>.
[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>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/info/rfc8259>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/info/rfc8288>.
Loffredo, et al. Expires November 28, 2019 [Page 20]
Internet-Draft RDAP Sorting and Paging May 2019
10.2. Informative References
[CURSOR] Nimesh, R., "Paginating Real-Time Data with Keyset
Pagination", July 2014, <https://www.sitepoint.com/
paginating-real-time-data-cursor-based-pagination/>.
[CURSOR-API1]
facebook.com, "facebook for developers - Using the Graph
API", July 2017, <https://developers.facebook.com/docs/
graph-api/using-graph-api>.
[CURSOR-API2]
twitter.com, "Pagination", 2017,
<https://developer.twitter.com/en/docs/ads/general/guides/
pagination.html>.
[GOESSNER-JSON-PATH]
Goessner, S., "JSONPath - XPath for JSON", 2007,
<http://goessner.net/articles/JsonPath/>.
[HATEOAS] Jedrzejewski, B., "HATEOAS - a simple explanation", 2018,
<https://www.e4developer.com/2018/02/16/
hateoas-simple-explanation/>.
[OData-Part1]
Pizzo, M., Handl, R., and M. Zurmuehl, "OData Version 4.0.
Part 1: Protocol Plus Errata 03", June 2016,
<http://docs.oasis-
open.org/odata/odata/v4.0/errata03/os/complete/part1-
protocol/
odata-v4.0-errata03-os-part1-protocol-complete.pdf>.
[REST] Fredrich, T., "RESTful Service Best Practices,
Recommendations for Creating Web Services", April 2012,
<http://www.restapitutorial.com/media/
RESTful_Best_Practices-v1_1.pdf>.
[RFC6901] Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed.,
"JavaScript Object Notation (JSON) Pointer", RFC 6901,
DOI 10.17487/RFC6901, April 2013,
<https://www.rfc-editor.org/info/rfc6901>.
[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>.
Loffredo, et al. Expires November 28, 2019 [Page 21]
Internet-Draft RDAP Sorting and Paging May 2019
[SEEK] EverSQL.com, "Faster Pagination in Mysql - Why Order By
With Limit and Offset is Slow?", July 2017,
<https://www.eversql.com/faster-pagination-in-mysql-why-
order-by-with-limit-and-offset-is-slow/>.
[W3C.CR-xpath-31-20161213]
Robie, J., Dyck, M., and J. Spiegel, "XML Path Language
(XPath) 3.1", World Wide Web Consortium CR CR-xpath-
31-20161213, December 2016,
<https://www.w3.org/TR/2016/CR-xpath-31-20161213>.
Appendix A. Change Log
00: Initial working group version ported from draft-loffredo-regext-
rdap-sorting-and-paging-05
01: Removed both "offset" and "nextOffset" to keep "paging_metadata"
consistent between the pagination methods. Renamed
"Considerations about Paging Implementation" section in ""cursor"
Parameter". Removed "FOR DISCUSSION" items. Provided a more
detailed description of both "sorting_metadata" and
"paging_metadata" objects.
02: Removed both "offset" and "limit" parameters. Added ABNF syntax
of cursor parameter. Rearranged the layout of some sections.
Removed some items from "Informative References" 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, et al. Expires November 28, 2019 [Page 22]
Internet-Draft RDAP Sorting and Paging May 2019
Scott Hollenbeck
Verisign Labs
12061 Bluemont Way
Reston, VA 20190
USA
Email: shollenbeck@verisign.com
URI: https://www.verisignlabs.com/
Loffredo, et al. Expires November 28, 2019 [Page 23]
Html markup produced by rfcmarkup 1.129c, available from
https://tools.ietf.org/tools/rfcmarkup/