RESTCONF Extensions to Support List Pagination
draft-wwlh-netconf-list-pagination-rc-02

Document Type Active Internet-Draft (individual)
Authors Kent Watsen  , Qin Wu  , Olof Hagsand  , Hongwei Li  , Per Andersson 
Last updated 2021-10-25
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NETCONF Working Group                                          K. Watsen
Internet-Draft                                           Watsen Networks
Updates: 8040 (if approved)                                        Q. Wu
Intended status: Standards Track                     Huawei Technologies
Expires: 28 April 2022                                        O. Hagsand
                                                                 Netgate
                                                                   H. Li
                                              Hewlett Packard Enterprise
                                                            P. Andersson
                                                           Cisco Systems
                                                         25 October 2021

             RESTCONF Extensions to Support List Pagination
                draft-wwlh-netconf-list-pagination-rc-02

Abstract

   This document defines a mapping of the list pagination mechanism
   defined in [I-D.wwlh-netconf-list-pagination] to RESTCONF [RFC8040].

   This document updates RFC 8040, to declare "list" and "leaf-list" as
   valid resource targets for the RESTCONF GET and DELETE operations, to
   define GET query parameters necessary for list pagination, and to
   define a media-type for XML-based lists.

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 28 April 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Updates to RFC 8040 . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Resource Targets  . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Media Type  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Query Parameters  . . . . . . . . . . . . . . . . . . . .   4
       2.3.1.  The "limit" Query Parameter . . . . . . . . . . . . .   5
       2.3.2.  The "offset" Query Parameter  . . . . . . . . . . . .   5
       2.3.3.  The "direction" Query Parameter . . . . . . . . . . .   5
       2.3.4.  The "sort-by" Query Parameter . . . . . . . . . . . .   6
       2.3.5.  The "where" Query Parameter . . . . . . . . . . . . .   6
       2.3.6.  The "sublist-limit" Query Parameter . . . . . . . . .   6
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  The "RESTCONF Capability URNs" Registry . . . . . . . . .   6
     3.2.  The "Media Types" Registry  . . . . . . . . . . . . . . .   7
       3.2.1.  Media Type "application/yang-data+xml-list" . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  Example YANG Module  . . . . . . . . . . . . . . . .   9
   Appendix B.  Example Data Set . . . . . . . . . . . . . . . . . .   9
   Appendix C.  Example Queries  . . . . . . . . . . . . . . . . . .   9
     C.1.  List pagination with all query parameters . . . . . . . .   9
     C.2.  Deletion of a list  . . . . . . . . . . . . . . . . . . .  11
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   This document defines a mapping of the list pagination mechanism
   defined in [I-D.wwlh-netconf-list-pagination] to RESTCONF [RFC8040].

   This document updates RFC 8040, as described in Section 2.

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   Declaring "list" and "leaf-list" as valid resource targets for the
   GET operation is necessary for list pagination.  Declaring these
   nodes as valid resource targets for the DELETE operation merely
   completes the solution for RESTCONF.

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

1.2.  Conventions

   Various examples used in this document use a placeholder value for
   binary data that has been base64 encoded (e.g., "BASE64VALUE=").
   This placeholder value is used as real base64 encoded structures are
   often many lines long and hence distracting to the example being
   presented.

2.  Updates to RFC 8040

2.1.  Resource Targets

   This document extends Section 3.5 of [RFC8040] to add "list" and
   "leaf-list" nodes (not just their entries) as valid data resources
   for the "GET" and "DELETE" operations.

2.2.  Media Type

   This document extends Section 3.2 of [RFC8040] to add a new media
   type, "application/yang-data+xml-list", to encode "list" and "leaf-
   list" nodes in XML.

   The "application/yang-data+xml-list" media-type defines a pseudo top-
   level element called "xml-list" that is used to wrap the response
   set, thus ensuring that a single top-level element is returned for
   the XML encoding", as required by Section 4.3 of [RFC8040].

   For JSON, the existing "application/yang-data+json" media type is
   sufficient, as the JSON format has built-in support for encoding
   arrays.

   The "application/yang-data+xml-list" media type is registered in
   Section 3.2.1.

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2.3.  Query Parameters

   This document extends Section 4.8 of [RFC8040] to add new query
   parameters "limit", "offset", "direction", "sort-by", "where", and
   "sublist-list".

   These six query parameters correspond to those defined in Sections
   3.1 and 3.2 in [I-D.wwlh-netconf-list-pagination].

   +-----------+---------+-----------------------------------------+
   | Name      | Methods | Description                             |
   +-----------+---------+-----------------------------------------+
   | limit     | GET,    | Limits the number of entries returned.  |
   |           | HEAD    | If not specified, the number of entries |
   |           |         | that may be returned is unbounded.      |
   |           |         |                                         |
   | offset    | GET,    | Indicates the number of entries in the  |
   |           | HEAD    | result set that should the skipped over |
   |           |         | when preparing the response.  If not    |
   |           |         | specified, then no entries in the       |
   |           |         | result set are skipped.                 |
   |           |         |                                         |
   | direction | GET,    | Indicates the direction that the result |
   |           | HEAD    | set is to be traversed.  If not         |
   |           |         | specified, then the result set is       |
   |           |         | traversed in the "forwards" direction.  |
   |           |         |                                         |
   | sort-by   | GET,    | Indicates the node name that the result |
   |           | HEAD    | set should be sorted by.  If not        |
   |           |         | specified, then the result set's        |
   |           |         | default order is used, per YANG's       |
   |           |         | "ordered-by" statement.                 |
   |           |         |                                         |
   | where     | GET,    | Specifies a filter expression that      |
   |           | HEAD    | result set entries must match.  If      |
   |           |         | not specified, then no entries are      |
   |           |         | filtered from the result set.           |
   |           |         |                                         |
   | sublist-  | GET,    | Limits the number of entries returned   |
   |  limit    | HEAD    | returned for descendent lists and       |
   |           |         | leaf-lists. If not specified, the       |
   |           |         | number of entries that may be returned  |
   |           |         | is unbounded.                           |
   +-----------+---------+-----------------------------------------+

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   For all of the query parameters, the query parameter is only allowed
   for the GET and HEAD methods on "list" and "leaf-list" data
   resources.  A "400 Bad Request" status-line MUST be returned if used
   with any other method or resource type.  The error-tag value
   "operation-not-supported" is used in this case.

   Per the conformance defined in Section 3.1 of
   [I-D.wwlh-netconf-list-pagination], all of these parameters MUST be
   supported for all lists and leaf-lists, but servers MAY disable the
   support for some or all "config false" lists, as described in
   Section 3.3 of [I-D.wwlh-netconf-list-pagination].

2.3.1.  The "limit" Query Parameter

   The "limit" query parameter corresponds to the "limit" parameter
   defined in Section 3.1.5 of [I-D.wwlh-netconf-list-pagination].

   If the limit value is invalid, then a "400 Bad Request" status-line
   MUST be returned with the error-type value "application" and error-
   tag value "invalid-value".

2.3.2.  The "offset" Query Parameter

   The "offset" query parameter corresponds to the "offset" parameter
   defined in Section 3.1.4 of [I-D.wwlh-netconf-list-pagination].

   If the offset value is invalid, a "400 Bad Request" status-line MUST
   be returned with the error-type value "application" and error-tag
   value "invalid-value".

   If the offset value exceeds the number of entries in the working
   result set, then a "416 Range Not Satisfiable" status-line MUST be
   returned with the error-type value "application", error-tag value
   "invalid-value", and SHOULD also include the "offset-out-of-range"
   identity as error-app-tag value.

2.3.3.  The "direction" Query Parameter

   The "direction" query parameter corresponds to the "direction"
   parameter defined in Section 3.1.3 of
   [I-D.wwlh-netconf-list-pagination].

   If the direction value is invalid, then a "400 Bad Request" status-
   line MUST be returned with the error-type value "application" and
   error-tag value "invalid-value".

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2.3.4.  The "sort-by" Query Parameter

   The "sort-by" query parameter corresponds to the "sort-by" parameter
   defined in Section 3.1.2 of [I-D.wwlh-netconf-list-pagination].

   If the specified node identifier is invalid, then a "400 Bad Request"
   status-line MUST be returned with the error-type value "application"
   and error-tag value "invalid-value".

2.3.5.  The "where" Query Parameter

   The "where" query parameter corresponds to the "where" parameter
   defined in Section 3.1.1 of [I-D.wwlh-netconf-list-pagination].

   If the specified XPath expression is invalid, then a "400 Bad
   Request" status-line MUST be returned with the error-type value
   "application" and error-tag value "invalid-value".

2.3.6.  The "sublist-limit" Query Parameter

   The "sublist-limit" query parameter corresponds to the "sublist-
   limit" parameter defined in Section 3.2.1 of
   [I-D.wwlh-netconf-list-pagination].

   If the sumlist-limit value is invalid, then a "400 Bad Request"
   status-line MUST be returned with the error-type value "application"
   and error-tag value "invalid-value".

3.  IANA Considerations

3.1.  The "RESTCONF Capability URNs" Registry

   This document registers six capabilities in the RESTCONF Capability
   URNs [RFC8040] maintained at https://www.iana.org/assignments/
   restconf-capability-urns/restconf-capability-urns.xhtml.  Following
   the instructions defined in Section 11.4 of [RFC8040], the below
   registrations are requested:

   All the registrations are to use this document (RFC XXXX) for the
   "Reference" value.

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   Index           Capability Identifier
   ---------------------------------------------------------------------
   :limit          urn:ietf:params:restconf:capability:limit:1.0
   :offset         urn:ietf:params:restconf:capability:offset:1.0
   :direction      urn:ietf:params:restconf:capability:direction:1.0
   :sort-by        urn:ietf:params:restconf:capability:sort-by:1.0
   :where          urn:ietf:params:restconf:capability:where:1.0
   :sublist-limit  urn:ietf:params:restconf:capability:sublist-limit:1.0

3.2.  The "Media Types" Registry

   This document registers one media type in the "application"
   subregistry of the Media Types registry [RFC6838] [RFC4855]
   maintained at https://www.iana.org/assignments/media-types/media-
   types.xhtml#application.  Following the format defined in [RFC4855],
   the below registration is requested:

3.2.1.  Media Type "application/yang-data+xml-list"

   Type name: application

      Subtype name: yang-data+xml-list

      Required parameters: None

      Optional parameters: None

      Encoding considerations: 8-bit
         Each conceptual YANG data node is encoded according to the
         XML Encoding Rules and Canonical Format for the specific
         YANG data node type defined in [RFC7950].

      Security considerations: Security considerations related
         to the generation and consumption of RESTCONF messages
         are discussed in Section 12 of RFC 8040.  Additional
         security considerations are specific to the semantics
         of particular YANG data models.  Each YANG module is
         expected to specify security considerations for the
         YANG data defined in that module.

      Interoperability considerations: RFC XXXX specifies the
         format of conforming messages and the interpretation
         thereof.

      Published specification: RFC XXXX

      Applications that use this media type: Instance document data
         parsers used within a protocol or automation tool that

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         utilize the YANG Patch data structure.

      Fragment identifier considerations: Fragment identifiers for
         this type are not defined.  All YANG data nodes are
         accessible as resources using the path in the request URI.

      Additional information:

         Deprecated alias names for this type: N/A
         Magic number(s): N/A
         File extension(s): None
         Macintosh file type code(s): "TEXT"

      Person & email address to contact for further information:
         See the Authors' Addresses section of RFC XXXX.

      Intended usage: COMMON

      Restrictions on usage: N/A

      Author: See the Authors' Addresses section of RFC XXXX.

      Change controller: Internet Engineering Task Force
         (mailto:iesg@ietf.org).

      Provisional registration? (standards tree only): no

4.  Security Considerations

   This document introduces protocol operations for paging through data
   already provided by the RESTCONF protocol, and hence does not
   introduce any new security considerations.

   This document does not define a YANG module and hence there are no
   data modeling considerations beyond those discussed in
   [I-D.wwlh-netconf-list-pagination].

5.  References

5.1.  Normative References

   [I-D.wwlh-netconf-list-pagination]
              "List Pagination...", <FIXME>.

   [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>.

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   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

5.2.  Informative References

   [I-D.ietf-netconf-restconf-collection]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Collection Resource", Work in Progress, Internet-Draft,
              draft-ietf-netconf-restconf-collection-00, 30 January
              2015, <https://datatracker.ietf.org/doc/html/draft-ietf-
              netconf-restconf-collection-00>.

   [RFC4855]  Casner, S., "Media Type Registration of RTP Payload
              Formats", RFC 4855, DOI 10.17487/RFC4855, February 2007,
              <https://www.rfc-editor.org/info/rfc4855>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/info/rfc6838>.

Appendix A.  Example YANG Module

   The examples within this document use the "example-social" YANG
   module defined in Appendix A.1 of [I-D.wwlh-netconf-list-pagination].

Appendix B.  Example Data Set

   The Example Data Set used by the examples is defined in Appendix A.2
   of [I-D.wwlh-netconf-list-pagination].

Appendix C.  Example Queries

C.1.  List pagination with all query parameters

   This example mimics that Appendix A.3.7 of
   [I-D.wwlh-netconf-list-pagination].

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   =============== NOTE: '\' line wrapping per RFC 8792 ================

   GET /restconf/ds/ietf-datastores:running/example-social:members/memb\
   er?where=//stats//joined[starts-with(@timestamp,'2020')]&sort-by=tim\
   estamp&direction=backwards&offset=2&limit=2&sublist-limit=1  HTTP/1.1
   Host: example.com
   Accept: application/yang-data+xml-list

   Response from the RESTCONF server:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   HTTP/1.1 200 OK
   Date: Thu, 26 Jan 2017 20:56:30 GMT
   Server: example-server
   Last-Modified: Thu, 26 Jan 2017 20:55:30 GMT
   Content-Type: application/yang-data+xml-list

   <lp:xml-list xmlns:lp="urn:ietf:params:xml:ns:yang:ietf-restconf-lis\
   t-pagination"
     xmlns="http://example.com/ns/example-social">
     <member lp:remaining="1">
       <member-id>eric</member-id>
       <email-address>eric@example.com</email-address>
       <password>$0$1543</password>
       <avatar>BASE64VALUE=</avatar>
       <tagline>Go to bed with dreams; wake up with a purpose.</tagline>
       <following>alice</following>
       <posts>
         <post>
           <timestamp>2020-09-17T18:02:04Z</timestamp>
           <title>Son, brother, husband, father</title>
           <body>What's your story?</body>
         </post>
       </posts>
       <favorites>
         <bits lp:remaining="2">two</bits>
       </favorites>
       <stats>
         <joined>2020-09-17T19:38:32Z</joined>
         <membership-level>pro</membership-level>
         <last-activity>2020-09-17T18:02:04Z</last-activity>
       </stats>
     </member>
     <member lp:remaining="1">
       <member-id>bob</member-id>
       <email-address>bob@example.com</email-address>
       <password>$0$1543</password>

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       <avatar>BASE64VALUE=</avatar>
       <tagline>Here and now, like never before.</tagline>
       <posts>
         <post lp:remaining="2">
           <timestamp>2020-08-14T03:32:25Z</timestamp>
           <body>Just got in.</body>
         </post>
       </posts>
       <favorites>
         <decimal64-numbers lp:remaining="1">3.14159</bits>
       </favorites>
       <stats>
         <joined>2020-08-14T03:30:00Z</joined>
         <membership-level>standard</membership-level>
         <last-activity>2020-08-14T03:34:30Z</last-activity>
       </stats>
     </member>
   </lp:xml-list>

C.2.  Deletion of a list

   This example illustrates using a "list" as the DELETE target.

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   DELETE /restconf/ds/ietf-datastores:running/example-social:members/m\
   ember=bob/favorites/decimal64-numbers HTTP/1.1
   Host: example.com
   Accept: application/yang-data+xml

   Response from the RESTCONF server:

   HTTP/1.1 204 No Content
   Date: Thu, 26 Jan 2017 20:56:30 GMT
   Server: example-server

Acknowledgements

   This work has benefited from the discussions of restconf resource
   collection over the years, in particular,
   [I-D.ietf-netconf-restconf-collection].  The authors additionally
   thank the following for lively discussions on list (ordered by first
   name): Andy Bierman, Martin Bjoerklund, and Robert Varga

Authors' Addresses

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   Kent Watsen
   Watsen Networks

   Email: kent+ietf@watsen.net

   Qin Wu
   Huawei Technologies
   101 Software Avenue, Yuhua District
   Nanjing
   Jiangsu, 210012
   China

   Email: bill.wu@huawei.com

   Olof Hagsand
   Netgate

   Email: olof@hagsand.se

   Hongwei Li
   Hewlett Packard Enterprise

   Email: flycoolman@gmail.com

   Per Andersson
   Cisco Systems

   Email: perander@cisco.com

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