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Versions: 00 01 02 03 04

Network Working Group                                         A. Bierman
Internet-Draft                                                 YumaWorks
Intended status: Standards Track                            M. Bjorklund
Expires: March 8, 2014                                    Tail-f Systems
                                                               K. Watsen
                                                        Juniper Networks
                                                             R. Fernando
                                                                   Cisco
                                                       September 4, 2013


                           RESTCONF Protocol
                   draft-bierman-netconf-restconf-00

Abstract

   This document describes a RESTful protocol that provides a
   programmatic interface over HTTP for accessing data defined in YANG,
   using the datastores defined in NETCONF.

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 http://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 March 8, 2014.

Copyright Notice

   Copyright (c) 2013 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
   (http://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



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Simple Subset of NETCONF Functionality . . . . . . . . . .  5
     1.2.  Data Model Driven API  . . . . . . . . . . . . . . . . . .  6
     1.3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  7
       1.3.1.  NETCONF  . . . . . . . . . . . . . . . . . . . . . . .  7
       1.3.2.  HTTP . . . . . . . . . . . . . . . . . . . . . . . . .  8
       1.3.3.  YANG . . . . . . . . . . . . . . . . . . . . . . . . .  8
       1.3.4.  Terms  . . . . . . . . . . . . . . . . . . . . . . . .  9
     1.4.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 10
       1.4.1.  Resource URI Map . . . . . . . . . . . . . . . . . . . 11
       1.4.2.  RESTCONF Message Examples  . . . . . . . . . . . . . . 11
   2.  Framework  . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     2.1.  Message Model  . . . . . . . . . . . . . . . . . . . . . . 18
     2.2.  Notification Model . . . . . . . . . . . . . . . . . . . . 18
     2.3.  Resource Model . . . . . . . . . . . . . . . . . . . . . . 18
       2.3.1.  RESTCONF Resource Types  . . . . . . . . . . . . . . . 18
       2.3.2.  Resource Discovery . . . . . . . . . . . . . . . . . . 19
     2.4.  Datastore Model  . . . . . . . . . . . . . . . . . . . . . 19
       2.4.1.  Content Model  . . . . . . . . . . . . . . . . . . . . 20
       2.4.2.  Editing Model  . . . . . . . . . . . . . . . . . . . . 20
       2.4.3.  Locking Model  . . . . . . . . . . . . . . . . . . . . 22
       2.4.4.  Persistence Model  . . . . . . . . . . . . . . . . . . 22
       2.4.5.  Defaults Model . . . . . . . . . . . . . . . . . . . . 22
     2.5.  Transaction Model  . . . . . . . . . . . . . . . . . . . . 23
     2.6.  Extensibility Model  . . . . . . . . . . . . . . . . . . . 23
     2.7.  Versioning Model . . . . . . . . . . . . . . . . . . . . . 23
     2.8.  Retrieval Filtering Model  . . . . . . . . . . . . . . . . 24
     2.9.  Access Control Model . . . . . . . . . . . . . . . . . . . 24
   3.  Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     3.1.  OPTIONS  . . . . . . . . . . . . . . . . . . . . . . . . . 25
     3.2.  HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
     3.3.  GET  . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     3.4.  POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
       3.4.1.  Create Resource Mode . . . . . . . . . . . . . . . . . 29
       3.4.2.  Invoke Operation Mode  . . . . . . . . . . . . . . . . 30
     3.5.  PUT  . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     3.6.  PATCH  . . . . . . . . . . . . . . . . . . . . . . . . . . 30
     3.7.  DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 31
     3.8.  Query Parameters . . . . . . . . . . . . . . . . . . . . . 31
       3.8.1.  "config" Parameter . . . . . . . . . . . . . . . . . . 31
       3.8.2.  "depth" Parameter  . . . . . . . . . . . . . . . . . . 32



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       3.8.3.  "format" Parameter . . . . . . . . . . . . . . . . . . 34
       3.8.4.  "insert" Parameter . . . . . . . . . . . . . . . . . . 35
       3.8.5.  "point" Parameter  . . . . . . . . . . . . . . . . . . 36
       3.8.6.  "select" Parameter . . . . . . . . . . . . . . . . . . 37
     3.9.  Protocol Operations  . . . . . . . . . . . . . . . . . . . 38
   4.  Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
     4.1.  Request URI Structure  . . . . . . . . . . . . . . . . . . 39
     4.2.  Message Headers  . . . . . . . . . . . . . . . . . . . . . 40
     4.3.  Message Encoding . . . . . . . . . . . . . . . . . . . . . 41
     4.4.  RESTCONF Meta-Data . . . . . . . . . . . . . . . . . . . . 41
       4.4.1.  JSON Encoding of RESTCONF Meta-Data  . . . . . . . . . 42
     4.5.  Return Status  . . . . . . . . . . . . . . . . . . . . . . 43
     4.6.  Message Caching  . . . . . . . . . . . . . . . . . . . . . 43
   5.  Resources  . . . . . . . . . . . . . . . . . . . . . . . . . . 45
     5.1.  API Resource (/.well-known/restconf) . . . . . . . . . . . 45
       5.1.1.  /.well-known/restconf/datastore  . . . . . . . . . . . 45
       5.1.2.  /.well-known/restconf/modules  . . . . . . . . . . . . 46
       5.1.3.  /.well-known/restconf/operations . . . . . . . . . . . 47
     5.2.  Datastore Resource . . . . . . . . . . . . . . . . . . . . 48
     5.3.  Data Resource  . . . . . . . . . . . . . . . . . . . . . . 48
       5.3.1.  Encoding YANG Instance Identifiers in the Request
               URI  . . . . . . . . . . . . . . . . . . . . . . . . . 49
       5.3.2.  Data Resource Retrieval  . . . . . . . . . . . . . . . 52
     5.4.  Operation Resource . . . . . . . . . . . . . . . . . . . . 52
       5.4.1.  Encoding Operation Input Parameters  . . . . . . . . . 53
       5.4.2.  Encoding Operation Output Parameters . . . . . . . . . 54
     5.5.  Event Resource . . . . . . . . . . . . . . . . . . . . . . 55
   6.  Error Reporting  . . . . . . . . . . . . . . . . . . . . . . . 56
     6.1.  Error Response Message . . . . . . . . . . . . . . . . . . 57
   7.  YANG Patch . . . . . . . . . . . . . . . . . . . . . . . . . . 59
     7.1.  Why not use JSON Patch?  . . . . . . . . . . . . . . . . . 59
     7.2.  YANG Patch Target Data Node  . . . . . . . . . . . . . . . 60
     7.3.  YANG Patch Edit Operations . . . . . . . . . . . . . . . . 60
     7.4.  YANG Patch Error Handling  . . . . . . . . . . . . . . . . 60
     7.5.  YANG Patch Response  . . . . . . . . . . . . . . . . . . . 61
     7.6.  YANG Patch Examples  . . . . . . . . . . . . . . . . . . . 61
       7.6.1.  Continue-on-error Example  . . . . . . . . . . . . . . 61
       7.6.2.  Move list entry example  . . . . . . . . . . . . . . . 64
   8.  RESTCONF module  . . . . . . . . . . . . . . . . . . . . . . . 66
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 79
     9.1.  Well-Known URI . . . . . . . . . . . . . . . . . . . . . . 79
     9.2.  YANG Module Registry . . . . . . . . . . . . . . . . . . . 79
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 80
   11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 81
     11.1. YANG-API-01 to RESTCONF-00 . . . . . . . . . . . . . . . . 81
   12. Closed Issues  . . . . . . . . . . . . . . . . . . . . . . . . 83
   13. Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 85
   14. Example YANG Module  . . . . . . . . . . . . . . . . . . . . . 86



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   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 91
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 91
     15.2. Informative References . . . . . . . . . . . . . . . . . . 92
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 93















































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1.  Introduction

   There is a need for standard mechanisms to allow WEB applications to
   access the configuration data, operational data, data-model specific
   protocol operations, and notification events within a networking
   device, in a modular and extensible manner.

   This document describes a RESTful protocol called RESTCONF, running
   over HTTP [RFC2616], for accessing data defined in YANG [RFC6020],
   using datastores defined in NETCONF [RFC6241].

   The NETCONF protocol defines configuration datastores and a set of
   Create, Retrieve, Update, Delete (CRUD) operations that can be used
   to access these datastores.  The YANG language defines the syntax and
   semantics of datastore content, operational data, custom protocol
   operations, and notification events.  RESTful operations are used to
   access the hierarchical data within a datastore.

   A RESTful API can be created that provides CRUD operations on a
   NETCONF datastore containing YANG-defined data.  This can be done in
   a simplified manner, compatible with HTTP and RESTful design
   principles.  Since NETCONF protocol operations are not relevant, the
   user should not need any prior knowledge of NETCONF in order to use
   the RESTful API.

   Configuration data and state data are exposed as resources that can
   be retrieved with the GET method.  Resources representing
   configuration data can be modified with the DELETE, PATCH, POST, and
   PUT methods.  Data-model specific protocol operations defined with
   the YANG "rpc" statement can be invoked with the POST method.  Data-
   model specific notification events defined with the YANG
   "notification" statement can be accessed (delivery method TBD).

1.1.  Simple Subset of NETCONF Functionality

   The framework and meta-model used for a RESTful API does not need to
   mirror those used by the NETCONF protocol.  It just needs to be
   compatible with NETCONF.  A simplified framework and protocol is
   needed that utilizes the three NETCONF datastores (candidate,
   running, startup), but hides the complexity of multiple datastores
   from the client.

   A simplified transaction model is needed that allows basic CRUD
   operations on a hierarchy of conceptual resources.  This represents a
   limited subset of the transaction capabilities of the NETCONF
   protocol.

   Applications that require more complex transaction capabilities might



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   consider NETCONF instead of RESTCONF.  The following transaction
   features are not directly provided in RESTCONF:

   o  datastore locking (full or partial)

   o  candidate datastore

   o  startup datastore

   o  validate operation

   o  confirmed-commit procedure

   It is possible that a server could expose NETCONF operations as data-
   model specific operation resources, but that is out of scope within
   this document.

   The RESTful API is not intended to replace NETCONF, but rather
   provide an additional simplified interface that follows RESTful
   principles and is compatible with a resource-oriented device
   abstraction.  It is expected that applications that need the full
   feature set of NETCONF such as notifications will continue to use
   NETCONF.

   The following figure shows the system components:

         +-----------+           +-----------------+
         |  WEB app  | <-------> |                 |
         +-----------+   HTTP    | network device  |
                                 |                 |
         +-----------+           |   +-----------+ |
         |  NMS app  | <-------> |   | datastore | |
         +-----------+  NETCONF  |   +-----------+ |
                                 +-----------------+

1.2.  Data Model Driven API

   RESTCONF combines the simplicity of a RESTful API over HTTP with the
   predictability and automation potential of a schema-driven API.

   A RESTful client using HATEOAS principles would not use any data
   modelling language to define the application-specific content of the
   API.  The client would discover each new child resource as it
   traverses the URIs return as Location IDs to discover the server
   capabilities.

   This approach has 3 significant weaknesses wrt/ control of complex
   networking devices:



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   o  inefficient performance: configuration APIs will be quite complex
      and may require thousands of protocol messages to discover all the
      schema information.  Typically the data type information has to be
      passed in the protocol messages, which is also wasteful overhead.

   o  no data model richness: without a data model, the schema-level
      semantics and validation constraints are not available to the
      application.

   o  no tool automation: API automation tools need some sort of content
      schema to function.  Such tools can automate various programming
      and documentation tasks related to specific data models.

   Data model modules such as YANG modules serve as an "API contract"
   that will be honored by the server.  An application designer can code
   to the data model, knowing in advance important details about the
   exact protocol operations and datastore content a conforming server
   implementation will support.

   RESTCONF provides the YANG module capability information supported by
   the server, in case the client wants to use it.  The URIs for custom
   protocol operations and datastore content are predictable, based on
   the YANG module definitions.  Note that the YANG modules and
   predictable URIs are optional to use by the client.  They can be
   completely ignored without any loss of protocol functionality.

   Operational experience with CLI and SNMP indicates that operators
   learn the 'location' of specific service or device related data and
   do not expect such information to be arbitrary and discovered each
   time the client opens a management session to a server.

1.3.  Terminology

   The keywords "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].

1.3.1.  NETCONF

   The following terms are defined in [RFC6241]:

   o  candidate configuration datastore

   o  client

   o  configuration data




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   o  datastore

   o  configuration datastore

   o  protocol operation

   o  running configuration datastore

   o  server

   o  startup configuration datastore

   o  state data

   o  user

1.3.2.  HTTP

   The following terms are defined in [RFC2616]:

   o  entity tag

   o  fragment

   o  header line

   o  message body

   o  method

   o  path

   o  query

   o  request URI

   o  response body

1.3.3.  YANG

   The following terms are defined in [RFC6020]:

   o  container

   o  data node

   o  key leaf




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   o  leaf

   o  leaf-list

   o  list

   o  presence container (or P-container)

   o  RPC operation (now called protocol operation)

   o  non-presence container (or NP-container)

   o  ordered-by system

   o  ordered-by user

1.3.4.  Terms

   The following terms are used within this document:

   o  API resource: a resource with the media type "application/
      vnd.yang.api+xml" or "application/vnd.yang.api+json".  API
      resources can only be edited by the server.

   o  data resource: a resource with the media type "application/
      vnd.yang.data+xml" or "application/vnd.yang.data+json".  Data
      resources can be edited by clients or the server.  Only YANG
      containers and lists can be data resources.  Top-level YANG
      terminals are treated as fields within the datastore resource.

   o  datastore resource: a resource with the media type "application/
      vnd.yang.datastore+xml" or "application/vnd.yang.datastore+json".
      Datastore resources can only be edited by the server.

   o  edit operation: a RESTCONF operation on a data resource using the
      POST, PUT, PATCH, or DELETE method.

   o  event resource: a resource with the media type "application/
      vnd.yang.event+xml" or "application/vnd.yang.event+json".  It
      represents a conceptual system or data-model specific event that
      is delivered within a notification message.

   o  field: a YANG terminal node within a resource.

   o  operation: the conceptual RESTCONF operation for a message,
      derived from the HTTP method, request URI, headers, and message
      body.




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   o  operation resource: a resource with the media type "application/
      vnd.yang.operation+xml" or "application/vnd.yang.operation+json".

   o  patch: a generic PATCH operation on the target datastore.  The
      media type of the message body content will identity the patch
      type in use.

   o  plain patch: a PATCH operation where the media type is
      "application/vnd.yang.data+xml" or "application/
      vnd.yang.data+json".

   o  query parameter: a parameter (and its value if any), encoded
      within the query portion of the request URI.

   o  resource: a conceptual object representing a manageable component
      within a device.  Refers to the resource itself of the resource
      and all its fields.

   o  retrieval request: an operation using the GET or HEAD methods.

   o  target resource: the resource that is associated with a particular
      message, identified by the "path" component of the request URI.

   o  unified datastore: A conceptual representation of the device
      running configuration.  The server will hide all NETCONF datastore
      details for edit operations, such as the ":candidate" and
      ":startup" capabilities.

   o  YANG Patch: a PATCH operation where the media type is
      "application/vnd.yang.patch+xml" or "application/
      vnd.yang.patch+json".

   o  YANG terminal node: a YANG node representing a leaf, leaf-list, or
      anyxml definition.

1.4.  Overview

   This document defines the RESTCONF protocol, a RESTful API for
   accessing conceptual datastores containing data defined with YANG
   language.  RESTCONF provides an application framework and meta-model,
   using HTTP methods.

   The RESTCONF resources are accessed via a set of URIs defined in this
   document.  The set of YANG modules supported by the server will
   determine the additional data model specific operations and top-level
   data node resources available on the server.





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1.4.1.  Resource URI Map

   The URI hierarchy for the RESTCONF resources consists of an entry
   point container, 3 top-level resources, and 1 field.  Refer to
   Section 5 for details on each URI.

     /.well-known/restconf
        /datastore
           /<top-level-data-nodes> (config=true or false)
        /modules
           /module
              /name
              /revision
              /namespace
              /feature
              /deviation
        /operations
           /<custom protocol operations>
        /version (field)

1.4.2.  RESTCONF Message Examples

   The examples within this document use the normative YANG module
   defined in Section 8 and the non-normative example YANG module
   defined in Section 14.

   This section shows some typical RESTCONF message exchanges.

1.4.2.1.  Retrieve the Top-level API Resource

   By default, when a resource is retrieved, any nested resources are
   also returned, using the default encoding, which is XML.

   The client may start by retrieving the top-level API resource, using
   the entry point URI "/.well-known/restconf".

      GET /.well-known/restconf?format=json HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.api+json

   The server might respond as follows:










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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server
      Content-Type: application/vnd.yang.api+json

      {
        "restconf": {
          "datastore" : [ null ],
          "modules": {
            "module": [
              {
                "name" : "example-jukebox",
                "revision" : "2013-09-04",
                "namespace" : "example.com"
              }
            ]
          },
          "operations" : {
             "play" : [ null ]
          },
          "version": "1.0"
        }
      }

   To request that the response content to be encoded in XML, the
   "Accept" header can be used, as in this example request:

      GET /.well-known/restconf HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.api+xml

   An alternate approach is provided using the "format" query parameter,
   as in this example request:

      GET /.well-known/restconf?format=xml HTTP/1.1
      Host: example.com

   The server will return the same response either way, which might be
   as follows :

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server
      Cache-Control: no-cache
      Pragma: no-cache
      Content-Type: application/vnd.yang.api+xml





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      <restconf xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
        <datastore />
        <modules>
          <module>
            <name>example-jukebox</name>
            <revision>2013-09-04</revision>
            <namespace>example.com</namespace>
          </module>
        </modules>
        <operations>
          <play xmlns="http://example.com/ns/example-jukebox" />
        </operations>
        <version>1.0</version>
      </restconf>

   Refer to Section 3.3 for details on the GET method.

1.4.2.2.  Create New Data Resources

   To create a new "jukebox" resource, the client might send:

      POST /.well-known/restconf/datastore HTTP/1.1
      Host: example.com
      Content-Type: application/vnd.yang.data+json

      { "example-jukebox:jukebox" : [null] }

   If the resource is created, the server might respond:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server
      Location: http://example.com/.well-known/restconf/datastore/
        example-jukebox:jukebox
      Last-Modified: Mon, 23 Apr 2012 17:01:00 GMT
      ETag: b3a3e673be2

   To create a new "artist" resource within the "library" resource, the
   client might send the following request.

      POST /.well-known/restconf/datastore/example-jukebox:jukebox/
         library HTTP/1.1
      Host: example.com
      Content-Type: application/vnd.yang.data+json

      { "artist" : {
          "name" : "Foo Fighters"
        }



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      }

   If the resource is created, the server might respond as follows.
   Note that the "Location" header line is wrapped for display purposes
   only:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2012 17:02:00 GMT
      Server: example-server
      Location: http://example.com/.well-known/restconf/datastore/
           example-jukebox:jukebox/library/artist/Foo%20Fighters
      Last-Modified: Mon, 23 Apr 2012 17:02:00 GMT
      ETag: b3830f23a4c

   To create a new "album" resource for this artist within the "jukebox"
   resource, the client might send the following request.  Note that the
   request URI header line is wrapped for display purposes only:

      POST /.well-known/restconf/datastore/example-jukebox:jukebox/
         library/artist/Foo%20Fighters  HTTP/1.1
      Host: example.com
      Content-Type: application/vnd.yang.data+json

      {
        "album" : {
          "name" : "Wasting Light",
          "genre" : "example-jukebox:Alternative",
          "year" : 2012   // note this is the wrong date
        }
      }

   If the resource is created, the server might respond as follows.
   Note that the "Location" header line is wrapped for display purposes
   only:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2012 17:03:00 GMT
      Server: example-server
      Location: http://example.com/.well-known/restconf/datastore/
        example-jukebox:jukebox/library/artist/Foo%20Fighters/
        album/Wasting%20Light
      Last-Modified: Mon, 23 Apr 2012 17:03:00 GMT
      ETag: b8389233a4c

   Refer to Section 3.4 for details on the POST method.






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1.4.2.3.  Replace an Existing Data Resource

   Note: replacing a resource is a fairly drastic operation.  The PATCH
   method is often more appropriate.

   The album sub-resource is replaced here for example purposes only.
   To replace the "album" resource contents, the client might send as
   follows.  Note that the request URI header line is wrapped for
   display purposes only:

      PUT /.well-known/restconf/datastore/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light   HTTP/1.1
      Host: example.com
      If-Match: b3830f23a4c
      Content-Type: application/vnd.yang.data+json

      {
        "album" : {
          "name" : "Wasting Light",
          "genre" : "example-jukebox:Alternative",
          "year" : 2011
        }
      }

   If the resource is updated, the server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:04:00 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 17:04:00 GMT
      ETag: b27480aeda4c

   Refer to Section 3.5 for details on the PUT method.

1.4.2.4.  Patch an Existing Data Resource

   To replace just the "year" field in the "album" resource (instead of
   replacing the entire resource), the client might send a plain patch
   as follows.  Note that the request URI header line is wrapped for
   display purposes only:

      PATCH /.well-known/restconf/datastore/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
      Host: example.com
      If-Match: b8389233a4c
      Content-Type: application/vnd.yang.data+json

      { "year" : 2011 }



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   If the field is updated, the server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:49:30 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 17:49:30 GMT
      ETag: b2788923da4c

   The XML encoding for the same request might be:

      PATCH /.well-known/restconf/datastore/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
      Host: example.com
      If-Match: b8389233a4c
      Content-Type: application/vnd.yang.data+xml


      <year xmlns="http://example.com/ns/example-jukebox">2011</year>

   Refer to Section 3.6 for details on the PATCH method.

1.4.2.5.  Delete an Existing Data Resource

   To delete a resource such as the "album" resource, the client might
   send:

      DELETE /.well-known/restconf/datastore/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
      Host: example.com

   If the resource is deleted, the server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:49:40 GMT
      Server: example-server

   Refer to Section 3.7 for details on the DELETE method.

1.4.2.6.  Delete an Optional Field Within a Data Resource

   The DELETE method cannot be used to delete an optional field within a
   resource.  This can only be done using the PATCH method with the YANG
   Patch media type.

   Refer to Section 7 for details on the YANG Patch method.






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1.4.2.7.  Invoke a Data Model Specific Operation

   To invoke a data-model specific operation via an operation resource,
   the POST method is used.  A client might send a "backup-datastore"
   request as follows:

      POST /.well-known/restconf/operations/example-ops:backup-datastore
          HTTP/1.1
      Host: example.com

   The server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:50:00 GMT
      Server: example-server

   Refer to Section 3.9 for details on using the POST method with
   operation resources.

































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2.  Framework

   The RESTCONF protocol defines a framework that can be used to
   implement a common API for configuration management.  This section
   describes the components of the RESTCONF framework.

2.1.  Message Model

   The RESTCONF protocol uses HTTP entities for messages.  A single HTTP
   message corresponds to a single protocol method.  Most messages can
   perform a single task on a single resource, such as retrieving a
   resource or editing a resource.  The exception is the PATCH method
   using the YANG Patch format.  This allows multiple datastore edits
   within a single message.

2.2.  Notification Model

      [TBD]

2.3.  Resource Model

   The RESTCONF protocol operates on a hierarchy of resources, starting
   with the top-level API resource itself.  Each resource represents a
   manageable component within the device.

   A resource can be considered a collection of conceptual data and the
   set of allowed methods on that data.  It can contain child nodes that
   are nested resources or fields.  The child resource types and methods
   allowed on them are data-model specific.

   A resource has its own media type identifier, represented by the
   "Content-Type" header in the HTTP response message.  A resource can
   contain zero or more nested resources.  A resource can be created and
   deleted independently of its parent resource, as long as the parent
   resource exists.

   All RESTCONF resources are defined in this document except datastore
   contents, protocol operations, and notification events.  The syntax
   and semantics for these resource types are defined with YANG
   statements.

2.3.1.  RESTCONF Resource Types

   The RESTCONF protocol defines some application specific media types
   to identify each of the available resource types.  The following
   table summarizes the purpose of each resource.





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              +-----------+--------------------------------+
              | Resource  | Media Type                     |
              +-----------+--------------------------------+
              | API       | application/vnd.yang.api       |
              | Datastore | application/vnd.yang.datastore |
              | Data      | application/vnd.yang.data      |
              | Event     | application/vnd.yang.event     |
              | Operation | application/vnd.yang.operation |
              | Patch     | application/vnd.yang.patch     |
              +-----------+--------------------------------+

                           RESTCONF Media Types

   These resources are described in Section 5.

2.3.2.  Resource Discovery

   A client SHOULD start by retrieving the top-level API resource, using
   the entry point URI "/.well-known/restconf".

   The RESTCONF protocol does not include a resource discovery
   mechanism.  Instead, the definitions within the YANG modules
   advertised by the server are used to construct a predictable
   operation or data resource identifier.

   The "depth" query parameter can be used to control how many
   descendant levels should be included when retrieving sub-resources.
   This parameter can be used with the GET method to discover sub-
   resources within a particular resource.

   Refer to Section 3.8.2 for more details on the "depth" parameter.

2.4.  Datastore Model

   A conceptual "unified datastore" is used to simplify resource
   management for the client.  The RESTCONF datastore is a combination
   of the running configuration and any non-configuration data supported
   by the device.  By default only configuration data is returned by a
   GET method on the datastore contents.

   The underlying NETCONF datastores can be used to implement the
   unified datastore, but the server design is not limited to the exact
   datastore procedures defined in NETCONF.

   The "candidate" and "startup" datastores are not visible in the
   RESTCONF protocol.  Transaction management and configuration
   persistence are handled by the server and not controlled by the
   client.



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2.4.1.  Content Model

   The RESTCONF protocol operates on a conceptual datastore defined with
   the YANG data modeling language.  The server lists each YANG module
   it supports in the "/.well-known/restconf/modules/module" resource in
   the top-level API resource type, using a structure based on the YANG
   module capability URI format defined in RFC 6020.

   The conceptual datastore contents, data-model-specific operations and
   notification events are identified by this set of YANG module
   resources.  All RESTCONF content identified as either a data
   resource, operation resource, or event resource is defined with the
   YANG language.

   The classification of data as configuration or non-configuration is
   derived from the YANG "config" statement.  Data retrieval with the
   GET method can be filtered in several ways, including the "config"
   parameter to retrieve configuration or non-configuration data.

   Data ordering behavior is derived from the YANG "ordered-by"
   statement.  The YANG Patch operation is provided to allow list or
   leaf-list fields to be inserted or moved in the same manner as
   NETCONF.

   The server is not required to maintain system ordered data in any
   particular persistent order.  The server SHOULD maintain the same
   data ordering for system ordered data until the next reboot or
   termination of the server.  The server MUST maintain the same data
   ordering for user ordered data until the next reboot or termination
   of the server.

2.4.2.  Editing Model

   The RESTCONF datastore editing model is simple and direct, similar to
   the behavior of the ":writable-running" capability in NETCONF.

   Each RESTCONF edit of a datastore resource is activated upon
   successful completion of the transaction.  It is an implementation-
   specific matter how the server accomplishes a RESTCONF edit request.
   For example, a server which only accepts edits through a candidate
   datastore may internally edit this datastore and perform the "commit"
   operation automatically.

   Applications which need more control over the editing model might
   consider using NETCONF instead of RESTCONF.






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2.4.2.1.  Edit Operation Discovery

   Sometimes a server does not implement every operation for every
   resource.  Sometimes data model requirements cause a node to
   implement a subset of the edit operations.  For example, a server may
   not allow modification of a particular configuration data node after
   the parent resource has been created.

   The OPTIONS method can be used to identify which HTTP methods are
   supported by the server for a particular resource.  For example, if
   the server will allow a data resource node to be created then the
   POST method will be returned in the response.

2.4.2.2.  Edit Collision Detection

   Two "edit collision detection" mechanisms are provided in RESTCONF,
   for datastore and data resources.

   o  timestamp: the last change time is maintained and the
      "Last-Modified" and "Date" headers are returned in the response
      for a retrieval request.  The "If-Unmodified-Since" header can be
      used in edit operation requests to cause the server to reject the
      request if the resource has been modified since the specified
      timestamp.

   o  entity tag: a unique opaque string is maintained and the "ETag"
      header is returned in the response for a retrieval request.  The
      "If-Match" header can be used in edit operation requests to cause
      the server to reject the request if the resource entity tag does
      not match the specified value.

   Note that the server is only required to maintain these properties
   for a datastore resource, not for individual data resources.

   Example:

   In this example, the server just supports the mandatory datastore
   last-changed timestamp.  The client has previously retrieved the
   "Last-Modified" header and has some value cached to provide in the
   following request to replace a list entry with key value "11":

     PATCH /.well-known/restconf/datastore/example-jukebox:jukebox/
       library/artist/Foo%20Fighters/album/Wasting%20Light/year HTTP/1.1
     Host: example.com
     Accept: application/vnd.yang.data+json
     If-Unmodified-Since: Mon, 23 Apr 2012 17:01:00 GMT
     Content-Type: application/vnd.yang.data+json




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     { "year" : "2011" }

   In this example the datastore resource has changed since the time
   specified in the "If-Unmodified-Since" header.  The server might
   respond:

      HTTP/1.1 304 Not Modified
      Date: Mon, 23 Apr 2012 19:01:00 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 17:45:00 GMT
      ETag: b34aed893a4c

2.4.3.  Locking Model

   Datastore locking is not provided by RESTCONF.  An application that
   needs to make several changes to the running configuration datastore
   contents in sequence, without disturbance from other clients might
   consider using the NETCONF protocol instead of RESTCONF.

2.4.4.  Persistence Model

   Each RESTCONF edit of a datastore resource is saved to non-volatile
   storage in an implementation-specific matter by the server.  There is
   no guarantee that configuration changes are saved immediately, or
   that the saved configuration is always a mirror of the running
   configuration.

   Applications which need more control over the persistence model might
   consider using NETCONF instead of RESTCONF.

2.4.5.  Defaults Model

   NETCONF has a rather complex defaults handling model for leafs.
   RESTCONF attempts to avoid this complexity by restricting the
   operations that can be applied to a resource.

   If the target of a GET method (plus "select" value) is a data node
   that represents a leaf that has a default value, and the leaf has not
   been given a value yet, the server MUST return the default value that
   is in use by the server.

   The GET method returns only descendant nodes that exist, which will
   be determined by the server.  There is no mechanism for the client to
   ask the server for the default values of nested resources that would
   be used for any nodes not present, but some default value is in use
   by the server.  (There is no retrieval mode like
   "with-defaults=report-all" in NETCONF.)




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   Applications which need more control over the defaults model might
   consider using NETCONF instead of RESTCONF.

2.5.  Transaction Model

   The RESTCONF protocol provides an extensible transaction framework
   that allows a simplified transaction model that uses plain REST
   operations to edit one resource (and sub-resources) at a time.  It
   also provides YANG Patch, which is a standard variant of the PATCH
   method.  This allows a richer set of edit operations that can be
   applied to multiple resources at once.

   RESTCONF does not provide a more complex transaction model that
   allows for multiple edits to be stored in a temporary scratchpad and
   committed all at once.

   Applications which need more control over the transaction model might
   consider using NETCONF instead of RESTCONF.

2.6.  Extensibility Model

   The RESTCONF protocol is designed to be extensible for datastore
   content and data-model specific protocol operations.  New protocol
   operations can be added without changing the entry point if they are
   optional and do not alter any existing operations.

   Separate namespaces for each YANG module are used.  Content encoded
   in XML will indicate the module using the "namespace" URI value in
   the YANG module.  Content encoded in JSON will indicate the module
   using the module name specified in the YANG module, but this is not
   required unless multiple sibling nodes have the same YANG identifier
   name.  JSON encoding rules for module names are specified in
   [I-D.lhotka-netmod-json].

2.7.  Versioning Model

   The version of a resource instance is identified with an entity tag,
   as defined by HTTP.  The version identifiers in this section apply to
   the version of the schema definition of a resource.  There are two
   types of schema versioning information used in the RESTCONF protocol:

   o  the RESTCONF protocol version

   o  data and operation resource definition versions

   The protocol version is identified by the string used for the well-
   known URI entry point "/.well-known/restconf".  This would be changed
   (e.g., "/.well-known/restconf2") if non-backward compatible changes



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   are ever needed.  Minor version changes that do not break backward-
   compatibility will not cause the entry point to change.

   The API "restconf/version" resource can be used by the client to
   identify the exact version of the RESTCONF protocol implemented by
   the server.  This value will include the complete RESTCONF protocol
   version.  The "/.well-known/restconf/version" resource MUST be
   updated every time the protocol specification is republished.

   The resource definition version for a data or operation resource is a
   date string, which is the revision date of the YANG module that
   defines the resource.  The resource version for all other resource
   types is a numeric string, defined by the "/.well-known/restconf/
   version" field.

2.8.  Retrieval Filtering Model

   There are three types of filtering for retrieval of data resources in
   the RESTCONF protocol.

   o  conditional all-or-nothing: use some conditional test mechanism in
      the request headers and retrieve either a complete "200 OK"
      response if the condition is met, or a "304 Not Modified" Status-
      Line if the condition is not met.

   o  data classification: request configuration or non-configuration
      data.

   o  filter: request a subset of all possible descendant nodes within
      the target resource.  The "select" query parameter can be used for
      this purpose.

   Refer to Section 5.3.2 for details on data retrieval filtering.

2.9.  Access Control Model

   The RESTCONF protocol provides no granular access control for any
   content except for operation and data resources.  The NETCONF Access
   Control Model (NACM) is defined in [RFC6536].  There is a specific
   mapping between RESTCONF operations and NETCONF edit operations,
   defined in Table 1.  The resource path also needs to be converted
   internally by the server to the corresponding YANG instance-
   identifier.  Using this information, the server can apply the NACM
   access control rules to RESTCONF messages.

   The server MUST NOT allow any operation to any resources that the
   client is not authorized to access.




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3.  Operations

   The RESTCONF protocol uses HTTP methods to identify the CRUD
   operation requested for a particular resource.  The following table
   shows how the RESTCONF operations relate to NETCONF protocol
   operations:

            +----------+-------------------------------------+
            | RESTCONF | NETCONF                             |
            +----------+-------------------------------------+
            | OPTIONS  | none                                |
            | HEAD     | none                                |
            | GET      | <get-config>, <get>                 |
            | POST     | <edit-config> (operation="create")  |
            | PUT      | <edit-config> (operation="replace") |
            | PATCH    | <edit-config> (operation="merge")   |
            | DELETE   | <edit-config> (operation="delete")  |
            +----------+-------------------------------------+

                     Table 1: CRUD Methods in RESTCONF

   The NETCONF "remove" operation attribute is not supported by the HTTP
   DELETE method.  The resource must exist or the DELETE method will
   fail.

   This section defines the RESTCONF protocol usage for each HTTP
   method.

3.1.  OPTIONS

   The OPTIONS method is sent by the client to discover which methods
   are supported by the server for a specific resource.  It is supported
   for all media types.  Note that implementation of this method is part
   of HTTP, and this section does not introduce any additional
   requirements.

   The request MUST contain a request URI that contains at least the
   entry point component.

   The server will return a "Status-Line" header containing "204 No
   Content". and include the "Allow" header in the response.  This
   header will be filled in, based on the target resource media type.
   Other headers MAY also be included in the response.

   Example 1:

   A client might request the methods supported for a data resource
   called "library":



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      OPTIONS /.well-known/restconf/datastore/example-jukebox:jukebox/
        library/artist   HTTP/1.1
      Host: example.com

   The server might respond (for a config=true list):

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server
      Allow: OPTIONS,HEAD,GET,POST,PUT,PATCH,DELETE

   Example 2:

   A client might request the methods supported for a non-configuration
   "counters" resource within a "system" resource:

      OPTIONS /.well-known/restconf/datastore/example-system:system/
         counters HTTP/1.1
      Host: example.com

   The server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:02:00 GMT
      Server: example-server
      Allow: OPTIONS,HEAD,GET

   Example 3:

   A client might request the methods supported for an operation
   resource called "play":

      OPTIONS /.well-known/restconf/operations/play HTTP/1.1
      Host: example.com

   The server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:02:00 GMT
      Server: example-server
      Allow: POST

3.2.  HEAD

   The HEAD method is sent by the client to retrieve just the headers
   that would be returned for the comparable GET method, without the
   response body.  It is supported for all resource types, except
   operation resources.



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   The request MUST contain a request URI that contains at least the
   entry point component.

   The same query parameters supported by the GET method are supported
   by the HEAD method.  For example, the "select" query parameter can be
   used to specify a nested resource within the target resource.

   The access control behavior is enforced as if the method was GET
   instead of HEAD.  The server MUST respond the same as if the method
   was GET instead of HEAD, except that no response body is included.

   Example:

   The client might request the response headers for JSON representation
   of the "library" resource:

      HEAD /.well-known/restconf/datastore/example-jukebox:jukebox/
          library HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.data+json

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:02:40 GMT
      Server: example-server
      Content-Type: application/vnd.yang.data+json
      Cache-Control: no-cache
      Pragma: no-cache
      ETag: a74eefc993a2b
      Last-Modified: Mon, 23 Apr 2012 11:02:14 GMT

3.3.  GET

   The GET method is sent by the client to retrieve data and meta-data
   for a resource.  It is supported for all resource types, except
   operation resources.  The request MUST contain a request URI that
   contains at least the entry point component.

   The following query parameters are supported by the GET method:

   +--------+---------+------------------------------------------------+
   | Name   | Section | Description                                    |
   +--------+---------+------------------------------------------------+
   | config | 3.8.1   | Request either configuration or                |
   |        |         | non-configuration data                         |
   | depth  | 3.8.2   | Control the depth of a retrieval request       |




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   | format | 3.8.3   | Request either JSON or XML content in the      |
   |        |         | response                                       |
   | select | 3.8.6   | Specify a nested resource within the target    |
   |        |         | resource                                       |
   +--------+---------+------------------------------------------------+

                           GET Query Parameters

   The server MUST NOT return any data resources for which the user does
   not have read privileges.

   If the user is not authorized to read any portion of the target
   resource, an error response containing a "403 Forbidden" Status-Line
   is returned to the client.

   If the user is authorized to read some but not all of the target
   resource, the unauthorized content is omitted from the response
   message body, and the authorized content is returned to the client.

   Example:

   The client might request the response headers for a JSON
   representation of the "library" resource:

      GET /.well-known/restconf/datastore/example-jukebox:jukebox/
        library/artist/Foo%20Fighters/album?format=json HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.api+json

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:02:40 GMT
      Server: example-server
      Content-Type: application/vnd.yang.data+json
      Cache-Control: no-cache
      Pragma: no-cache
      ETag: a74eefc993a2b
      Last-Modified: Mon, 23 Apr 2012 11:02:14 GMT

      {
        "album" : {
          "name" : "Wasting Light",
          "genre" : "example-jukebox:Alternative",
          "year" : 2011
        }
      }




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3.4.  POST

   The POST method is sent by the client for various reasons.  The
   server uses the target resource media type to determine how to
   process the request.

   The request MUST contain a request URI that contains a target
   resource which identifies one of the following resource types:

      +-----------+------------------------------------------------+
      | Type      | Description                                    |
      +-----------+------------------------------------------------+
      | Datastore | Create a top-level configuration data resource |
      | Data      | Create a configuration data sub-resource       |
      | Operation | Invoke protocol operation                      |
      +-----------+------------------------------------------------+

                     Resource Types that Support POST

3.4.1.  Create Resource Mode

   If the target resource type is a Datastore or Data resource, then the
   POST is treated as a request to create a resource or sub-resource.

   The following query parameters are supported by the POST method for
   Datastore and Data resource types.  They can only be used for YANG
   list data nodes which are ordered by the user.

      +--------+---------+-----------------------------------------+
      | Name   | Section | Description                             |
      +--------+---------+-----------------------------------------+
      | insert | 3.8.4   | Specify where to insert a resource      |
      | point  | 3.8.5   | Specify the insert point for a resource |
      +--------+---------+-----------------------------------------+

                           POST Query Parameters

   If the POST method succeeds, a "204 No Content" Status-Line is
   returned and there is no response message body.

   If the user is not authorized to create the target resource, an error
   response containing a "403 Forbidden" Status-Line is returned to the
   client.  All other error responses are handled according to the
   procedures defined in Section 6.







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3.4.2.  Invoke Operation Mode

   If the target resource type is an Operation resource, then the POST
   method is treated as a request to invoke that operation.  The message
   body (if any) is processed as the operation input parameters.  Refer
   to Section 5.4 for details on Operation resources.

   If the POST method succeeds, a "200 OK" Status-Line is returned if
   there is a response message body, and a "204 No Content" Status-Line
   is returned if there is no response message body.

   If the user is not authorized to invoke the target operation, an
   error response containing a "403 Forbidden" Status-Line is returned
   to the client.  All other error responses are handled according to
   the procedures defined in Section 6.

3.5.  PUT

   The PUT method is sent by the client to replace the target resource.

   The request MUST contain a request URI that contains a target
   resource that identifies the data resource to replace.

   If the PUT method succeeds, a "200 OK" Status-Line is returned, and
   there is no response message body.

   If the user is not authorized to replace the target resource an error
   response containing a "403 Forbidden" Status-Line is returned to the
   client.  All other error responses are handled according to the
   procedures defined in Section 6.

3.6.  PATCH

   The PATCH method uses the HTTP PATCH method defined in [RFC5789] to
   provide an extensible framework for resource patching mechanisms.
   Each patch type needs a unique media type.  Any number of patch types
   can be supported by the server.  There are two mandatory patch types
   that MUST be implemented by the server:

   o  plain patch type: If the specified media type is "application/
      vnd.yang.data", then the PATCH method is a simple merge operation
      on the target resource.  The message body contains the XML or JSON
      encoded resource content that will be merged with the target
      resource.

   o  YANG Patch type: If the specified media type is "application/
      vnd.yang.patch", then the PATCH method is a YANG Patch formatted
      list of edits (see Section 7).  The message body contains the XML



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      or JSON encoded instance of the 'patch' container specified in the
      'ietf-restconf' YANG module (see Section 8).

   The PATCH method MUST be used to create or delete an optional field
   within an existing resource or sub-resource.

   If the PATCH method succeeds, a "200 OK" Status-Line is returned, and
   there is no response message body.

   If the user is not authorized to alter the target resource an error
   response containing a "403 Forbidden" Status-Line is returned to the
   client.  All other error responses are handled according to the
   procedures defined in Section 6.

3.7.  DELETE

   The DELETE method is used to delete the target resource.

   If the DELETE method succeeds, a "200 OK" Status-Line is returned,
   and there is no response message body.

   If the user is not authorized to delete the target resource then an
   error response containing a "403 Forbidden" Status-Line is returned
   to the client.  All other error responses are handled according to
   the procedures defined in Section 6.

3.8.  Query Parameters

   Each RESTCONF operation allows zero or more query parameters to be
   present in the request URI.  Refer to Section 3 for details on the
   query parameters used in the definition of each operation.

   Query parameters can be given in any order.  Each parameter can
   appear zero or one time.  A default value may apply if the parameter
   is missing.

   This section defines all the RESTCONF query parameters.

3.8.1.  "config" Parameter

   The "config" parameter is used to specify whether configuration or
   non-configuration data is requested.

   This parameter is only supported for the GET and HEAD methods.  It is
   also only supported if the target resource is a data resource.

        syntax: config= true | false
        default: true



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   Example:

   This example request by the client would retrieve only the non-
   configuration data nodes that exist within the "library" resource.

      GET /.well-known/restconf/datastore/example-jukebox:jukebox/
        library?config=false   HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.data+json

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:01:30 GMT
      Server: example-server
      Cache-Control: no-cache
      Pragma: no-cache
      Content-Type: application/vnd.yang.data+json

      {
        "library" : {
           "artist-count" : 42,
           "album-count" : 59,
           "song-count" : 374
        }
      }

3.8.2.  "depth" Parameter

   The "depth" parameter is used to specify the number of nest levels
   returned in a response for a GET method.  A nest-level consists of
   the target resource and any child nodes which are contained within
   the target resource node.

   The start level is determined by the target resource for the
   operation.

        syntax: depth=<range: 1..max> | unbounded
        default: unbounded

   Example:

   This example operation would retrieve 2 levels of configuration data
   nodes that exist within the top-level "jukebox" resource.

      GET /.well-known/restconf/datastore/example-jukebox:jukebox
          ?depth=2 HTTP/1.1
      Host: example.com



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      Accept: application/vnd.yang.data+json

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:11:30 GMT
      Server: example-server
      Cache-Control: no-cache
      Pragma: no-cache
      Content-Type: application/vnd.yang.data+json

      {
        "jukebox" : {
          "library" : {
            "artist" : {
              "name" : "Foo Fighters"
            }
          },
          "player" : {
            "gap" : 0.5
          }
        }
      }

   By default, the server will include all sub-trees within a retrieved
   resource, which is the same resource type.  Only only level of sub-
   resources with a different media type than the target resource will
   be returned.

   For example, if the client retrieves the "application/vnd.yang.api"
   resource type, then the node for the datastore resource is returned
   as an empty node, because all its child nodes are data resources.
   The entire contents of the datastore are not returned in this case.
   The operation resources also are returned as empty nodes (e.g. "play"
   operation).

   Request URL:

      GET /.well-known/restconf HTTP/1.1

   Response:










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      {
        "restconf": {
          "datastore" : [ null ],
          "modules": {
            "module": [
              {
                "name" : "example-jukebox",
                "revision" : "2013-09-04",
                "namespace" : "example.com"
              }
            ]
          },
          "operations" : {
             "play" : [ null ]
          },
          "version": "1.0"
        }
      }

3.8.3.  "format" Parameter

   The "format" parameter is used to specify the format of any content
   returned in the response.  Note that this parameter MAY be used
   instead of the "Accept" header to identify the format desired in the
   response.

   The "format" parameter is only supported for the GET and HEAD
   methods.  It is supported for all RESTCONF media types.

        syntax: format= xml | json
        default: Accept header, then xml

   If the "format" parameter is present, then it overrides the Accept
   header, if present.  If neither the Accept header or the "format"
   parameter are present, then the default is XML.

   Examples:

      GET /.well-known/restconf/datastore/example-routing:routing
          HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.data+json

   This example request would retrieve only the configuration data nodes
   that exist within the top-level "routing" resource, and retrieve them
   in JSON encoding.





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      GET /.well-known/restconf/datastore/example-routing:routing
          ?format=json HTTP/1.1
      Host: example.com

   This example request would retrieve only the configuration data nodes
   that exist within the top-level "routing" resource, and retrieve them
   in JSON encoding.

3.8.4.  "insert" Parameter

   The "insert" parameter is used to specify how a resource should be
   inserted within a user-ordered list.

   This parameter is only supported for the POST method.  It is also
   only supported if the target resource is a data resource, and that
   data represents a YANG list that is ordered by the user, not the
   system.

   If the values "before" or "after" are used, then a "point" parameter
   for the insertion parameter MUST also be present.

        syntax: insert= first | last | before | after
        default: last

   Example:


























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    Request from client:

      PATCH /.well-known/restconf/datastore/example-jukebox:jukebox/
        playlist/Foo-One?insert=first HTTP/1.1
      Host: example.com
      Content-Type: application/vnd.yang.data+json

      {
        "song" : {
           "index" : 1,
           "id" : "/example-jukebox:jukebox/library/artist/
               Foo%20Fighters/album/Wasting%20Light/song/Rope"
         }
      }

    Response from server:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2012 13:01:20 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
      Location: http://example.com/.well-known/restconf/datastore/
         example-jukebox:jukebox/playlist/Foo-One/song/1
      ETag: eeeada438af

3.8.5.  "point" Parameter

   The "point" parameter is used to specify the insertion point for a
   data resource that is being created or moved within a user ordered
   list.  It is ignored unless the "insert" query parameter is also
   present, and has the value "before" or "after".

   This parameter contains the instance identifier of the resource to be
   used as the insertion point for a POST method.  It is encoded
   according to the rules defined in Section 5.3.1.  There is no default
   for this parameter.

      syntax: point= <instance-identifier of insertion point node>

   Example:

   In this example, the client is inserting a new "song" resource within
   an "album" resource after another song.  The request URI is split for
   display purposes only.







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   Request from client:

     POST /.well-known/restconf/datastore/example-jukebox:jukebox/
        library/artist/Foo%20Fighters/album/Wasting%20Light?insert=after
        &point=/.well-known/restconf/datastore/example-jukebox:jukebox/
        library/artist/Foo%20Fighters/album/Wasting%20Light/song/
        Bridge%20Burning   HTTP/1.1
     Host: example.com
     Content-Type: application/vnd.yang.data+json

     {
       "song" : {
          "name" : "Rope",
          "location" : "/media/rope.mp3",
          "format" : "MP3",
          "length" : 259
       }
     }

   Response from server:

     HTTP/1.1 204 No Content
     Date: Mon, 23 Apr 2012 13:01:20 GMT
     Server: example-server
     Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
     ETag: abcada438af

3.8.6.  "select" Parameter

   The "select" query parameter is used to specify an expression which
   can represent a subset of all data nodes within the target resource.
   It contains a relative path expression, using the target resource as
   the context node.

   It is supported for all resource types except operation resources.
   The contents are encoded according to the "api-select" rule defined
   in Section 5.3.1.  This parameter is only allowed for GET and HEAD
   methods.

   [FIXME: the syntax of the select string is still TBD; XPath, schema-
   identifier, regular expressions, something else; Perhaps add
   parameter "xselect" for XPath and this param is limited to a path-
   expr.]

   In this example the client is retrieving the API version field from
   the server in JSON format:





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      GET /.well-known/restconf?select=version&format=json HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.api+json

   The server might respond as follows.

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server
      Cache-Control: no-cache
      Pragma: no-cache
      Last-Modified: Sun, 22 Apr 2012 01:00:14 GMT
      Content-Type: application/vnd.yang.api+json

      { "version": "1.0" }

3.9.  Protocol Operations

   The RESTCONF protocol allows data-model specific protocol operations
   to be invoked using the POST method.  The media type "application/
   vnd.yang.operation+xml" or "application/vnd.yang.operation+json" MUST
   be used in the "Content-Type" line in the message header.

   Data model specific operations are supported.  The syntax and
   semantics of these operations exactly correspond to the YANG "rpc"
   statement definition for the operation.

   Refer to Section 5.4 for details on operation resources.























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4.  Messages

   This section describes the messages that are used in the RESTCONF
   protocol.

4.1.  Request URI Structure

   Resources are represented with URIs following the structure for
   generic URIs in [RFC3986].

   A RESTCONF operation is derived from the HTTP method and the request
   URI, using the following conceptual fields:

        <OP> /.well-known/restconf/<path>?<query>#<fragment>


         ^              ^             ^        ^         ^
         |              |             |        |         |
       method         entry       resource  query    fragment

         M              M            O        O         I

       M=mandatory, O=optional, I=ignored


       <text> replaced by client with real values

   o  method: the HTTP method identifying the RESTCONF operation
      requested by the client, to act upon the target resource specified
      in the request URI.  RESTCONF operation details are described in
      Section 3.

   o  entry: the well-known RESTCONF entry point ("/.well-known/
      restconf").

   o  resource: the path expression identifying the resource that is
      being accessed by the operation.  If this field is not present,
      then the target resource is the API itself, represented by the
      media type "application/vnd.yang.api".

   o  query: the set of parameters associated with the RESTCONF message.
      These have the familiar form of "name=value" pairs.  There is a
      specific set of parameters defined, although the server MAY choose
      to support additional parameters not defined in this document.

   o  fragment: This field is not used by the RESTCONF protocol.

   The client SHOULD NOT assume the final structure of a URI path for a



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   resource.  Instead, existing resources can be discovered with the GET
   method.  When new resources are created by the client, a "Location"
   header is returned, which identifies the path of the newly created
   resource.  The client MUST use this exact path identifier to access
   the resource once it has been created.

   The "target" of an operation is a resource.  The "path" field in the
   request URI represents the target resource for the operation.

4.2.  Message Headers

   There are several HTTP header lines utilized in RESTCONF messages.
   Messages are not limited to the HTTP headers listed in this section.

   HTTP defines which header lines are required for particular
   circumstances.  Refer to each operation definition section in
   Section 3 for examples on how particular headers are used.

   There are some request headers that are used within RESTCONF, usually
   applied to data resources.  The following tables summarize the
   headers most relevant in RESTCONF message requests:

   +---------------------+---------------------------------------------+
   | Name                | Description                                 |
   +---------------------+---------------------------------------------+
   | Accept              | Response Content-Types that are acceptable  |
   | Content-Type        | The media type of the request body          |
   | Host                | The host address of the server              |
   | If-Match            | Only perform the action if the entity       |
   |                     | matches ETag                                |
   | If-Modified-Since   | Only perform the action if modified since   |
   |                     | time                                        |
   | If-Unmodified-Since | Only perform the action if un-modified      |
   |                     | since time                                  |
   +---------------------+---------------------------------------------+

                         RESTCONF Request Headers

   The following tables summarize the headers most relevant in RESTCONF
   message responses:











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   +---------------+---------------------------------------------------+
   | Name          | Description                                       |
   +---------------+---------------------------------------------------+
   | Allow         | Valid actions when 405 error returned             |
   | Content-Type  | The media type of the response body               |
   | Date          | The date and time the message was sent            |
   | ETag          | An identifier for a specific version of a         |
   |               | resource                                          |
   | Last-Modified | The last modified date and time of a resource     |
   | Location      | The resource identifier for a newly created       |
   |               | resource                                          |
   +---------------+---------------------------------------------------+

                         RESTCONF Response Headers

4.3.  Message Encoding

   RESTCONF messages are encoded in HTTP according to RFC 2616.  The
   "utf-8" character set is used for all messages.  RESTCONF message
   content is sent in the HTTP message body.

   Content is encoded in either JSON or XML format.

   XML encoding rules for data nodes are defined in [RFC6020].  The same
   encoding rules are used for all XML content.

   JSON encoding rules are defined in [I-D.lhotka-netmod-json].  Plain
   JSON cannot be used because special encoding rules are needed to
   handle multiple module namespaces and provide consistent data type
   processing.

   Request input content encoding format is identified with the Content-
   Type header.  This field MUST be present if a message body is sent by
   the client.

   Response output content encoding format is identified with the Accept
   header, the "format" query parameter, or if neither is specified, the
   request input encoding format is used.  If there was no request
   input, then the default output encoding is XML.  File extensions
   encoded in the request are not used to identify format encoding.

4.4.  RESTCONF Meta-Data

   The RESTCONF protocol needs to retrieve the same meta-data that is
   used in the NETCONF protocol.  Information about default leafs, last-
   modified timestamps, etc. are commonly used to annotate
   representations of the datastore contents.  This meta-data is not
   defined in the YANG schema because it applies to the datastore, and



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   is common across all data nodes.

   This information is encoded as attributes in XML, but JSON does not
   have a standard way of attaching non-schema defined meta-data to a
   resource or field.

4.4.1.  JSON Encoding of RESTCONF Meta-Data

   The YANG to JSON mapping [I-D.lhotka-netmod-json] does not support
   attributes because YANG does not support meta-data in data node
   definitions.  This section specifies how RESTCONF meta-data is
   encoded in JSON.

   Only simple meta-data is supported:

   o  A meta-data instance can appear 0 or 1 times for a particular data
      node

   o  A meta-data instance associated with a resource is encoded as if
      it were a YANG leaf of type "string", according to the encoding
      rules in [I-D.lhotka-netmod-json], except the identifier is
      prepended with a "@" (%40) character.

   o  A meta-data instance associated with a field within a resource is
      encoded as if it were a container for the meta-data values and the
      field value in its native encoding.  It is encoded according to
      the rules in [I-D.lhotka-netmod-json], except the meta-data
      identifiers are prepended with a "@" (%40) character.  The field
      name/value pair is repeated inside this container, which contains
      the actual value of the field.

   Examples:

      Meta-data:

        enabled=<boolean>
        owner=<owner-name>

      YANG example:

        container top {
          leaf A {
            type int32;
          }
          leaf B {
            type boolean;
          }
        }



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   The client is retrieving the "top" data resource, and the server is
   including datastore meta-data.  Note that a query parameter to
   request or suppress specific meta-data is not provided in RESTCONF.

      GET /.well-known/restconf/datastore/example:top HTTP/1.1
      Host: example.com
      Accept: application/vnd.yang.api+json

   The server might respond as follows:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server
      Content-Type: application/vnd.yang.api+json

      {
        "top": {
          "@enabled" : "true",
          "@owner" : "fred",
          "A" : {
            "@enabled" : "true",
            "A" : 42
          },
          "B" : {
            "@enabled" : "false",
            "B" : true
          }
        }
      }

4.5.  Return Status

   Each message represents some sort of resource access.  An HTTP
   "Status-Line" header line is returned for each request.  If a 4xx or
   5xx range status code is returned in the Status-Line, then the error
   information will be returned in the response, according to the format
   defined in Section 6.1.

4.6.  Message Caching

   Since the datastore contents change at unpredictable times, responses
   from a RESTCONF server generally SHOULD NOT be cached.

   The server SHOULD include a "Cache-Control" header in every response
   that specifies whether the response should be cached.  A "Pragma"
   header specifying "no-cache" MAY also be sent in case the
   "Cache-Control" header is not supported.




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   Instead of using HTTP caching, the client SHOULD track the "ETag"
   and/or "Last-Modified" headers returned by the server for the
   datastore resource (or data resource if the server supports it).  A
   retrieval request for a resource can include headers such as
   "If-None-Match" or "If-Modified-Since" which will cause the server to
   return a "304 Not Modified" Status-Line if the resource has not
   changed.  The client MAY use the HEAD method to retrieve just the
   message headers, which SHOULD include the "ETag" and "Last-Modified"
   headers, if this meta-data is maintained for the target resource.










































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5.  Resources

   The resources used in the RESTCONF protocol are identified by the
   "path" component in the request URI.  Each operation is performed on
   a target resource.

5.1.  API Resource (/.well-known/restconf)

   The API resource contains the state and access points for the
   RESTCONF features.

   It is the top-level resource and has the media type "application/
   vnd.yang.api+xml" or "application/vnd.yang.api+json".  It is
   accessible through the well-known relative URI "/.well-known/
   restconf".

   There is one mandatory field "version" that identifies the specific
   version of the RESTCONF protocol implemented by the server:

   o  The same server-wide response MUST be returned each time this
      field is retrieved.

   o  It is assigned by the server when the server is started.

   o  The server MUST return the value "1.0" for this version of the
      RESTCONF protocol.

   o  This field is encoded with the rules for an "enumeration" data
      type, using the "version" leaf definition in Section 8.

   This resource has the following child resources:

            +----------------+--------------------------------+
            | Child Resource | Description                    |
            +----------------+--------------------------------+
            | datastore      | Link to "datastore" resource   |
            | modules        | YANG module capability URIs    |
            | operations     | Data-model specific operations |
            +----------------+--------------------------------+

                            RESTCONF Resources

5.1.1.  /.well-known/restconf/datastore

   This mandatory resource represents the running configuration
   datastore and any non-configuration data available.  It may be
   retrieved and edited directly.  It cannot be created or deleted by
   the client.  This resource type is defined in Section 5.2.



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5.1.2.  /.well-known/restconf/modules

   This mandatory resource contains the identifiers for the YANG data
   model modules supported by the server.

   The server MUST maintain a last-modified timestamp for this resource,
   and return the "Last-Modified" header when this resource is retrieved
   with the GET or HEAD methods.

   The server SHOULD maintain an entity-tag for this resource, and
   return the "ETag" header when this resource is retrieved with the GET
   or HEAD methods.

5.1.2.1.  /.well-known/restconf/modules/module

   This mandatory resource contains one URI string for each YANG data
   model module supported by the server.  There MUST be an instance of
   this resource for every YANG module that is accessible via an
   operation resource or a data resource.

   The contents of the "module" list are defined in the "module" YANG
   list statement in Section 8.

   The server MAY maintain a last-modified timestamp for each instance
   of this resource, and return the "Last-Modified" header when this
   resource is retrieved with the GET or HEAD methods.  If not supported
   then the timestamp for the parent "modules" resource MAY be used
   instead.

   The server MAY maintain an entity-tag for each instance of this
   resource, and return the "ETag" header when this resource is
   retrieved with the GET or HEAD methods.  If not supported then the
   timestamp for the parent "modules" resource MAY be used instead.

   The contents of this resource are encoded with the "uri" derived type
   from the "ietf-iana-types" modules in [RFC6991].

   There are additional encoding requirements for this resource.  The
   URI MUST follow the YANG module capability URI formatting defined in
   section 5.6.4 of [RFC6020].

5.1.2.2.  Retrieval Example

   In this example the client is retrieving the modules resource from
   the server in JSON format:

      GET /.well-known/restconf/modules&format=json HTTP/1.1
      Host: example.com



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      Accept: application/vnd.yang.api+json

   The server might respond as follows.

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server
      Cache-Control: no-cache
      Pragma: no-cache
      Last-Modified: Sun, 22 Apr 2012 01:00:14 GMT
      Content-Type: application/vnd.yang.api+json

      {
        "modules": {
          "module": [
            {
              "name" : "foo",
              "revision" : "2012-01-02",
              "namespace" : "http://example.com/ns/foo",
              "feature" : [ "feature1", "feature2" ]
            },
            {
              "name" : "foo-types",
              "revision" : "2012-01-05",
              "namespace" : "http://example.com/ns/foo-types"
            },
            {
              "name" : "bar",
              "revision" : "2012-11-05",
              "namespace" : "http://example.com/ns/bar",
              "feature" : [ "bar-ext" ]
            }
          ]
        }
      }

5.1.3.  /.well-known/restconf/operations

   This optional resource provides access to the data-model specific
   protocol operations supported by the server.  The server MAY omit
   this resource if no data-model specific operations are advertised.

   Any data-model specific operations defined in the YANG modules
   advertised by the server MAY be available as child nodes of this
   resource.






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5.2.  Datastore Resource

   A datastore resource represents the conceptual root of a tree of data
   resources.

   The server MUST maintain a last-modified timestamp for this resource,
   and return the "Last-Modified" header when this resource is retrieved
   with the GET or HEAD methods.  Only changes to configuration data
   resources within the datastore affect this timestamp.

   The server SHOULD maintain a resource entity tag for this resource,
   and return the "ETag" header when this resource is retrieved with the
   GET or HEAD methods.  The resource entity tag SHOULD be changed to a
   new previously unused value if changes to any configuration data
   resources within the datastore are made.

   A datastore resource can be retrieved with the GET method, to
   retrieve either configuration data resources or non-configuration
   data resources within the datastore.  The "config" query parameter is
   used to choose between them.  Refer to Section 3.8.1 for more
   details.

   The depth of the subtrees returned in retrieval operations can be
   controlled with the "depth" query parameter.  The number of nest
   levels, starting at the target resource, can be specified, or an
   unlimited number can be returned.  Refer to Section 3.8.2 for more
   details.

   [FIXME: not clear if top-level YANG data nodes MUST be containers or
   lists.

   A datastore resource can only be written directly with the PATCH
   method.  Only the configuration data resources within the datastore
   resource can be edited directly with all methods.]

5.3.  Data Resource

   A data resource represents a YANG data node that is a descendant node
   of a datastore resource.  Only YANG container and list data node
   types are considered to represent data resources.  Other YANG data
   nodes are considered to be fields within their parent resource.

   For configuration data resources, the server MAY maintain a last-
   modified timestamp for the resource, and return the "Last-Modified"
   header when it is retrieved with the GET or HEAD methods.

   For configuration data resources, the server MAY maintain a resource
   entity tag for the resource, and return the "ETag" header when it is



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   retrieved as the target resource with the GET or HEAD methods.  The
   resource entity tag SHOULD be changed to a new previously unused
   value if changes to the resource or any configuration resource within
   the resource is altered.

   A data resource can be retrieved with the GET method, to retrieve
   either configuration data resources or non-configuration data
   resources within the target resource.  The "config" query parameter
   is used to choose between them.  Refer to Section 3.8.1 for more
   details.

   The depth of the subtrees returned in retrieval operations can be
   controlled with the "depth" query parameter.  The number of nest
   levels, starting at the target resource, can be specified, or an
   unlimited number can be returned.  Refer to Section 3.8.2 for more
   details.

   A configuration data resource can be altered by the client with some
   of all of the edit operations, depending on the target resource and
   the specific operation.  Refer to Section 3 for more details on edit
   operations.

5.3.1.  Encoding YANG Instance Identifiers in the Request URI

   In YANG, data nodes are named with an absolute XPath expression, from
   the document root to the target resource.  In RESTCONF, URL friendly
   path expressions are used instead.

   The YANG "instance-identifier" (i-i) data type is represented in
   RESTCONF with the path expression format defined in this section.

           +-------+-------------------------------------------+
           | Name  | Comments                                  |
           +-------+-------------------------------------------+
           | point | Insertion point is always a full i-i      |
           | path  | Request URI path is a full or partial i-i |
           +-------+-------------------------------------------+

               RESTCONF instance-identifier Type Conversion

   The "path" component of the request URI contains the absolute path
   expression that identifies the target resource.  The "select" query
   parameter is used to optionally identify the requested data nodes
   within the target resource to be retrieved in a GET method.

   A predictable location for a data resource is important, since
   applications will code to the YANG data model module, which uses
   static naming and defines an absolute path location for all data



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   nodes.

   A RESTCONF data resource identifier is not an XPath expression.  It
   is encoded from left to right, starting with the top-level data node,
   according to the "api-path" rule in Section 5.3.1.1.  The node name
   of each ancestor of the target resource node is encoded in order,
   ending with the node name for the target resource.

   If the "select" is present, it is encoded, starting with a child node
   of the target resource, according to the "api-select" rule defined in
   Section 5.3.1.1.

   If a data node in the path expression is a YANG list node, then the
   key values for the list (if any) are encoded according to the
   "key-value" rule.  If the list node is the target resource, then the
   key values MAY be omitted, according to the operation.  For example,
   the POST method to create a new data resource for a list node does
   not allow the key values to be present in the request URI.

   The key leaf values for a data resource representing a YANG list MUST
   be encoded as follows:

   o  The value of each leaf identified in the "key" statement is
      encoded in order.

   o  All the components in the "key" statement MUST be encoded.
      Partial instance identifiers are not supported.

   o  Each value is encoded using the "key-value" rule in
      Section 5.3.1.1, according to the encoding rules for the data type
      of the key leaf.

   o  An empty string can be a valid key value (e.g., "/top/list/key1//
      key3").

   o  The "/" character MUST be URL-encoded (i.e., "%2F").

   o  All whitespace MUST be URL-encoded.

   o  A "null" value is not allowed since the "empty" data type is not
      allowed for key leafs.

   o  The XML encoding is defined in [RFC6020].

   o  The JSON encoding is defined in [I-D.lhotka-netmod-json].

   o  The entire "key-value" MUST be properly URL-encoded, according to
      the rules defined in [RFC3986].



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   o  resource URI values returned in Location headers for data
      resources SHOULD identify the module name, even if there are no
      conflicting local names when the resource is created.  This
      insures the correct resource will be identified even if the server
      loads a new module that the old client does not know about.

   Examples:

      [ lines wrapped for display purposes only ]

     /.well-known/restconf/datastore/example-jukebox:jukebox/library/
        artist/Beatles&select=album

     /.well-known/restconf/datastore/example-list:newlist/
        17&select=nextlist/22/44/acme-list-ext:ext-leaf

     /.well-known/restconf/datastore/example-list:somelist/
        fred%20and%20wilma

     /.well-known/restconf/datastore/example-list:somelist/
        fred%20and%20wilma/address

5.3.1.1.  ABNF For Data Resource Identifiers

   The following ABNF syntax is used to construct RESTCONF path
   identifiers:

       api-path = "/" api-identifier
                       0*("/" (api-identifier | key-value ))

       [FIXME: the syntax for the select string is still TBD]
       api-select = api-identifier
                       0*("/" (api-identifier | key-value ))

       api-identifier = [module-name ":"] identifier

       module-name = identifier

       key-value = string

       ;; An identifier MUST NOT start with
       ;; (('X'|'x') ('M'|'m') ('L'|'l'))
       identifier  = (ALPHA / "_")
                     *(ALPHA / DIGIT / "_" / "-" / ".")

       string = <an unquoted string>





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5.3.2.  Data Resource Retrieval

   There are three types of filtering for retrieval of data resources.
   This section defines each mode.

5.3.2.1.  Conditional Retrieval

   The HTTP headers (such as "If-Modified-Since" and "If-Match") can by
   used in for a request message for a GET method to check a condition
   within the server state, such as the last time the datastore resource
   was modified, or the resource entity tag of the target resource.

   If the condition is met according to the header definition, a "200
   OK" Status-Line and the data requested is returned in the response
   message.  If the condition is not met, a "304 Not Modified" Status-
   Line is returned in response message instead.

5.3.2.2.  Data Classification Retrieval

   The "config" query parameter can be used with the GET method to
   specify whether configuration or non-configuration data is requested.
   Refer to Section 3.8.1 for more details on the "config" query
   parameter.

5.3.2.3.  Filtered Retrieval

   The "select" query parameter is used to specify a filter that should
   be applied to the target resource to request a subset of all possible
   descendant nodes within the target resource.

   The format of the "select" parameter string is defined in
   Section 3.8.6.  The set of nodes selected by the filter expression is
   applied to each context node identified by the target resource.

5.4.  Operation Resource

   An operation resource represents an protocol operation defined with
   the YANG "rpc" statement.

   All operation resources share the same module namespace as any top-
   level data resources, so the name of an operation resource cannot
   conflict with the name of a top-level data resource defined within
   the same module.

   If 2 different YANG modules define the same "rpc" identifier, then
   the module name MUST be used in the request URI.  For example, if
   "module-A" and "module-B" both defined a "reset" operation, then
   invoking the operation from "module-A" would be requested as follows:



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      POST /.well-known/restconf/operations/module-A:reset HTTP/1.1
      Server example.com

   Any usage of an operation resource from the same module, with the
   same name, refers to the same "rpc" statement definition.  This
   behavior can be used to design protocol operations that perform the
   same general function on different resource types.

   If the "rpc" statement has an "input" section, then a message body
   MAY be sent by the client in the request, otherwise the request
   message MUST NOT include a message body.  If the "rpc" statement has
   an "output" section, then a message body MAY be sent by the server in
   the response.  Otherwise the server MUST NOT include a message body
   in the response message, and MUST send a "204 No Content" Status-Line
   instead.

5.4.1.  Encoding Operation Input Parameters

   If the "rpc" statement has an "input" section, then the "input" node
   is provided in the message body, corresponding to the YANG data
   definition statements within the "input" section.

   Example:

   The following YANG definition is used for the examples in this
   section.

       rpc reboot {
         input {
           leaf delay {
             units seconds;
             type uint32;
             default 0;
           }
           leaf message { type string; }
           leaf language { type string; }
         }
       }

   The client might send the following POST request message:











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      POST /.well-known/restconf/datastore/operations/
         example-ops:reboot HTTP/1.1
      Host: example.com
      Content-Type: application/vnd.yang.data+json

      {
        "input" : {
          "delay" : 600,
          "message" : "Going down for system maintenance",
          "language" : "en-US"
        }
      }

   The server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 25 Apr 2012 11:01:00 GMT
      Server: example-server

5.4.2.  Encoding Operation Output Parameters

   If the "rpc" statement has an "output" section, then the "output"
   node is provided in the message body, corresponding to the YANG data
   definition statements within the "output" section.

   Example:

   The following YANG definition is used for the examples in this
   section.

       rpc get-reboot-info {
         output {
           leaf reboot-time {
             units seconds;
             type uint32;
           }
           leaf message { type string; }
           leaf language { type string; }
         }
       }

   The client might send the following POST request message:

      POST /.well-known/restconf/datastore/operations/
         example-ops:get-reboot-info HTTP/1.1
      Host: example.com
      Content-Type: application/vnd.yang.data+json




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   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 25 Apr 2012 11:10:30 GMT
      Server: example-server

      {
        "output" : {
          "reboot-time" : 30,
          "message" : "Going down for system maintenance",
          "language" : "en-US"
        }
      }

5.5.  Event Resource

     [TBD]


































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6.  Error Reporting

   HTTP Status-Lines are used to report success or failure for RESTCONF
   operations.  The <rpc-error> element returned in NETCONF error
   responses contains some useful information.  This error information
   is adapted for use in RESTCONF, and error information is returned for
   "4xx" class of status codes.

   The following table summarizes the return status codes used
   specifically by RESTCONF operations:

   +---------------------------+---------------------------------------+
   | Status-Line               | Description                           |
   +---------------------------+---------------------------------------+
   | 100 Continue              | POST accepted, 201 should follow      |
   | 200 OK                    | Success with response body            |
   | 201 Created               | POST to create a resource success     |
   | 202 Accepted              | POST to create a resource accepted    |
   | 204 No Content            | Success without response body         |
   | 304 Not Modified          | Conditional operation not done        |
   | 400 Bad Request           | Invalid request message               |
   | 403 Forbidden             | Access to resource denied             |
   | 404 Not Found             | Resource target or resource node not  |
   |                           | found                                 |
   | 405 Method Not Allowed    | Method not allowed for target         |
   |                           | resource                              |
   | 409 Conflict              | Resource or lock in use               |
   | 413 Request Entity Too    | too-big error                         |
   | Large                     |                                       |
   | 414 Request-URI Too Large | too-big error                         |
   | 415 Unsupported Media     | non RESTCONF media type               |
   | Type                      |                                       |
   | 500 Internal Server Error | operation-failed                      |
   | 501 Not Implemented       | unknown-operation                     |
   | 503 Service Unavailable   | Recoverable server error              |
   +---------------------------+---------------------------------------+

                    HTTP Status Codes used in RESTCONF

   Since an operation resource is defined with a YANG "rpc" statement, a
   mapping between the NETCONF <error-tag> value and the HTTP status
   code is needed.  The specific error condition and response code to
   use are data-model specific and might be contained in the YANG
   "description" statement for the "rpc" statement.







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                 +-------------------------+-------------+
                 | <error-tag>             | status code |
                 +-------------------------+-------------+
                 | in-use                  | 409         |
                 | invalid-value           | 400         |
                 | too-big                 | 413         |
                 | missing-attribute       | 400         |
                 | bad-attribute           | 400         |
                 | unknown-attribute       | 400         |
                 | bad-element             | 400         |
                 | unknown-element         | 400         |
                 | unknown-namespace       | 400         |
                 | access-denied           | 403         |
                 | lock-denied             | 409         |
                 | resource-denied         | 409         |
                 | rollback-failed         | 500         |
                 | data-exists             | 409         |
                 | data-missing            | 409         |
                 | operation-not-supported | 501         |
                 | operation-failed        | 500         |
                 | partial-operation       | 500         |
                 | malformed-message       | 400         |
                 +-------------------------+-------------+

                   Mapping from error-tag to status code

6.1.  Error Response Message

   When an error occurs for a request message on a data resource or an
   operation resource, and a "4xx" class of status codes (except for
   status code "403"), then the server SHOULD send a response body
   containing the information described by the "errors" container
   definition within the YANG module Section 8.

   Example:

   The following example shows an error returned for an "lock-denied"
   error on a datastore resource.

      POST /.well-known/restconf/operations/lock-datastore HTTP/1.1
      Host: example.com

   The server might respond:








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      HTTP/1.1 409 Conflict
      Date: Mon, 23 Apr 2012 17:11:00 GMT
      Server: example-server
      Content-Type: application/vnd.yang.api+json

      {
        "errors": {
          "error": {
            "error-type": "protocol",
            "error-tag": "lock-denied",
            "error-message": "Lock failed, lock is already held",
          }
        }
      }





































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7.  YANG Patch

   The YANG Patch operation is provided so complex editing operations
   can be performed within RESTCONF.  The "plain patch" operation only
   provides a simple merge edit operation on the target datastore.

   A "YANG Patch" is an ordered list of edits that are applied to the
   target datastore by the server.  The specific fields are defined with
   the 'yang-patch' container definition in the YANG module Section 8.

   Each patch is identified by a client provided string, called the
   "patch-id".

   The client can control the type of error handling that should be
   applied to the list of supplied edits.

7.1.  Why not use JSON Patch?

   The RESTCONF PATCH method requires that the media type of the patch
   content be specified, so it should be possible to use any patch
   mechanism, including JSON Patch [RFC6902].

   The RESTCONF protocol is designed to utilize the YANG data modelling
   language to specify content schemas.  The JSON Patch mechanism is
   incompatible with RESTCONF for the following reasons:

   o  A patch mechanism that works with either XML or JSON encoding is
      needed.

   o  YANG configuration nodes can be named with complex keys, using one
      or more key leafs.  JSON arrays are packed and all the YANG keys
      would be collapsed down to a single integer index.

   o  YANG configuration nodes are named with stable, persistent
      identifiers, using key leafs.  JSON arrays are packed, and if
      entry I is added or deleted, then all entries I+1 ..  Imax are
      renumbered.

   o  The edit operation set needs to align with the NETCONF protocol,
      and JSON Patch does not provide an aligned set of edit operations.

   o  The datastore validation procedures need to be specific and
      aligned with YANG validation procedures.

   o  The error reporting needs to align with the NETCONF protocol, and
      JSON Patch does not provide an aligned error reporting mechanism.





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7.2.  YANG Patch Target Data Node

   The target data node for each edit operation is determined by the
   value of the target resource in the request and the "target" leaf
   within each "edit" entry.

   If the target resource specified in the request URI identifies a
   datastore resource, then the path string in the "target" leaf is an
   absolute path expression.  The first node specified in the "target"
   leaf is a top-level data node defined within a YANG module.

   If the target resource specified in the request URI identifies a data
   resource, then the path string in the "target" leaf is a relative
   path expression.  The first node specified in the "target" leaf is a
   child node of the data node associated with the target resource.

7.3.  YANG Patch Edit Operations

   Each YANG patch edit specifies one edit operation on the target data
   node.  The set of operations is aligned with the NETCONF edit
   operations, but also includes some new operations.

   +-----------+-------------------------------------------------------+
   | Operation | Description                                           |
   +-----------+-------------------------------------------------------+
   | create    | create a new data resource if it does not already     |
   |           | exist or error                                        |
   | delete    | delete a data resource if it already exists or error  |
   | insert    | insert a new user-ordered data resource               |
   | merge     | merge the edit value with the target data resource;   |
   |           | create if it does not already exist                   |
   | move      | re-order the target data resource                     |
   | replace   | replace the target data resource with the edit value  |
   | remove    | remove a data resource if it already exists or no     |
   |           | error                                                 |
   +-----------+-------------------------------------------------------+

                        YANG Patch Edit Operations

7.4.  YANG Patch Error Handling

   There are three error handling modes available that the server MUST
   support.  These modes specify how the server will behave when errors
   occur in the processing of each edit operation.  Note that the server
   MUST ensure that a well-formed message is received and that the
   supplied message body conforms to the YANG schema definition for the
   "patch" container, defined in the YANG module Section 8.




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   If a well-formed, schema-valid YANG Patch message is received, then
   then the server will process the supplied edits in ascending order.
   The following error modes apply to the processing of this edit list:

   o  all-or-none: All the specified edits MUST be applied or the target
      datastore contents SHOULD be returned to its original state before
      the PATCH method started.  The server MAY fail to restore the
      contents of the target datastore completely and with certainty.
      It is possible for a rollback to fail or and "undo" operation to
      fail.

   o  stop-on-error: Each edit will be attempted in order and if an
      error occurs, the the server will stop processing the edit list
      and return an error report identifying the edit list entry that
      caused the error.

   o  continue-on-error: Each edit will be attempted in order and if an
      error occurs, the the server will record an error identifying the
      edit list entry that caused the error, and continue to the next
      edit entry.

   The server will save the running datastore to non-volatile storage if
   it has changed, after the edits have been attempted.

7.5.  YANG Patch Response

   A special response is returned for YANG Patch operations, in order to
   report status information for each individual edit.  It is possible
   to report general errors as well.  The YANG conceptual container
   definition "yang-patch-status" defined in Section 8 is used to define
   the syntax.

7.6.  YANG Patch Examples

7.6.1.  Continue-on-error Example

   The following example shows several songs being added to an existing
   album.

   o  Each edit contains one song.

   o  The first song already exists, so an error will be reported for
      that edit.

   o  The error-action is continue-on-error, so the rest of the songs
      will be added without error.





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   Request from client:

     PATCH /.well-known/restconf/datastore/example-jukebox:jukebox/
        library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
     Host: example.com
     Content-Type: application/vnd.yang.patch+json

     {
       "yang-patch" : {
         "patch-id" : "add-songs-patch",
         "error-action" : "continue-on-error",
         "edit" : [
           {
             "edit-id" : 1,
             "operation" : "create",
             "target" : "/song",
             "value" : {
               "song" : {
                 "name" : "Bridge Burning",
                 "location" : "/media/bridge_burning.mp3",
                 "format" : "MP3",
                 "length" : 288
               }
             }
           },
           {
             "edit-id" : 2,
             "operation" : "create",
             "target" : "/song",
             "value" : {
               "song" : {
                 "name" : "Rope",
                 "location" : "/media/rope.mp3",
                 "format" : "MP3",
                 "length" : 259
               }
             }
           },
           {
             "edit-id" : 3,
             "operation" : "create",
             "target" : "/song",
             "value" : {
               "song" : {
                 "name" : "Dear Rosemary",
                 "location" : "/media/dear_rosemary.mp3",
                 "format" : "MP3",
                 "length" : 269



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               }
             }
           }
         ]
       }
     }

   Response from server:

     HTTP/1.1 409 Conflict
     Date: Mon, 23 Apr 2012 13:01:20 GMT
     Server: example-server
     Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
     Content-Type: application/vnd.yang.api+json

     {
       "yang-patch-status" : {
         "patch-id" : "add-songs-patch",
         "edit-status" : {
           "edit" : [
             {
               "edit-id" : 1,
               "errors" : {
                 "error" : {
                 "error-type": "application",
                 "error-tag": "data-exists",
                 "error-path": "/example-jukebox:jukebox/library/artist/
                    Foo%20Fighters/album/Wasting%20Light/song/
                    Burning%20Light",
                 "error-message": "Data already exists, cannot be
                  created"
               }
             },
             {
               "edit-id" : 2,
               "location" : "http://example.com/.well-known/restconf/
                  datastore/example-jukebox:jukebox/library/artist/
                  Foo%20Fighters/album/Wasting%20Light/song/Rope"
             },
             {
               "edit-id" : 3,
               "location" : "http://example.com/.well-known/restconf/
                  datastore/example-jukebox:jukebox/library/artist/
                  Foo%20Fighters/album/Wasting%20Light/song/
                  Dear%20Rosemary"
             }
           }
         ]



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       }
     }
   }

7.6.2.  Move list entry example

   The following example shows a song being moved within an existing
   playlist.  Song "1" in playlist "Foo-One" is being moved after song
   "3" in the playlist.  The operation succeeds, so a non-error reply
   example can be shown.









































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    Request from client:

      PATCH /.well-known/restconf/datastore/example-jukebox:jukebox/
        playlist/Foo-One   HTTP/1.1
      Host: example.com
      Content-Type: application/vnd.yang.patch+json

      {
        "yang-patch" : {
          "patch-id" : "move-song-patch",
          "error-action" : "all-or-none",
          "edit" : [
            {
              "edit-id" : 1,
              "operation" : "move",
              "target" : "/song/1",
              "point" : "/song3",
              "where" : "after"
            }
          ]
        }
      }

    Response from server:

      HTTP/1.1 400 OK
      Date: Mon, 23 Apr 2012 13:01:20 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
      Content-Type: application/vnd.yang.api+json

      {
        "yang-patch-status" : {
          "patch-id" : "move-song-patch",
          "edit-status" : {
            "edit" : [
              {
                "edit-id" : 1,
                "ok" : [ null ]
              }
            }
          ]
        }
      }
    }






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8.  RESTCONF module

   RFC Ed.: update the date below with the date of RFC publication and
   remove this note.

   <CODE BEGINS> file "ietf-restconf@2013-09-04.yang"

   module ietf-restconf {
     // RFC Ed.: replace XXXX with 'ietf' and remove this note
     namespace "urn:XXXX:params:xml:ns:yang:ietf-restconf";
     prefix "restconf";

     import ietf-yang-types { prefix yang; }
     import ietf-inet-types { prefix inet; }

     organization
       "IETF NETCONF (Network Configuration) Working Group";

     contact
       "Editor:   Andy Bierman
                  <mailto:andy@yumaworks.com>

        Editor:   Martin Bjorklund
                  <mailto:mbj@tail-f.com>

        Editor:   Kent Watsen
                  <mailto:kwatsen@juniper.net>

        Editor:   Rex Fernando
                  <mailto:rex@cisco.com>";

     description
       "This module contains conceptual YANG specifications
        for the YANG Patch and error content that is used in
        RESTCONF protocol messages. A conceptual container
        representing the RESTCONF API nodes (type vnd.yang.api).

        Note that the YANG definitions within this module do not
        represent configuration data of any kind.
        The YANG grouping statements provide a normative syntax
        for XML and JSON message encoding purposes.

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

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Simplified BSD License



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        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

     // RFC Ed.: replace XXXX with actual RFC number and remove this
     // note.

     // RFC Ed.: remove this note
     // Note: extracted from draft-bierman-netconf-restconf-00.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2013-09-04 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: RESTCONF Protocol.";
     }

     typedef data-resource-identifier {
       type string {
         length "1 .. max";
       }
       description
         "Contains a Data Resource Identifier formatted string
          to identify a specific data node.";
       reference
         "RFC XXXX: [sec. 5.3.1.1 ABNF For Data Resource Identifiers]";
     }

     // this typedef is TBD; not currently used
     typedef datastore-identifier {
       type union {
         type enumeration {
           enum candidate {
             description
               "Identifies the NETCONF shared candidate datastore.";
             reference
               "RFC 6241, section 8.3";
           }
           enum running {
             description
               "Identifies the NETCONF running datastore.";
             reference
               "RFC 6241, section 5.1";



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           }
           enum startup {
             description
               "Identifies the NETCONF startup datastore.";
             reference
               "RFC 6241, section 8.7";
           }
         }
         type string;
       }
       description
         "Contains a string to identify a specific datastore.
          The enumerated datastore identifier values are
          reserved for standard datastore names.";
     }

     grouping yang-patch {

       description
         "A grouping that contains a YANG container
          representing the syntax and semantics of a
          YANG Patch edit request message.";

       container yang-patch {
         description
           "Represents a conceptual sequence of datastore edits,
            called a patch. Each patch is given a client-assigned
            patch identifier. A patch is applied with client-specified
            error handling to control how the ordered list of edits
            is applied if an error is encountered.

            A patch MUST be validated by the server to be a
            well-formed message before any of the patch edits
            are validated or attempted.

            The validation model for patches closely follows
            the constraint enforcement model in YANG, except it
            is conceptually enforced on an ordered list of edits.

            The server MUST conceptually perform field validation
            for each edit in ascending order, as defined in RFC 6020,
            section 8.3.1 and 8.3.2.  This is most relevant if the edit
            error-action is 'stop-on-error', since the identification
            of the first error determines where edit processing is
            terminated.

            If YANG datastore validation (defined in RFC 6020, section 
            8.3.3) is required, then it performed after all edits have



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            been individually validated.

            It is possible for a datastore constraint violation to occur
            due to any node in the datastore, including nodes not
            included in the edit list. Any validation errors SHOULD
            be reported in the reply message.

            If datastore validation is required and fails, the server
            SHOULD NOT allow the datastore to remain invalid. It is an
            implementation-specific matter how the server fixes the
            invalid datastore.  For example, the server might prune
            invalid nodes causing the datastore validation error,
            or undo the entire patch.";

         reference
           "RFC 6020, section 8.3.";

         leaf patch-id {
           type string;
           description
             "An arbitrary string provided by the client to identify
              the entire patch.  This value SHOULD be present in any
              audit logging records generated by the server for the
              patch. Error messages returned by the server pertaining
              to this patch will be identified by this patch-id value.";
         }

         leaf error-action {
           type enumeration {
             enum all-or-none {
               description
                 "The server will apply all edits in the patch only
                  if no errors occur.  If any errors occur then
                  none of the edits will be applied and the
                  contents of the target datastore MUST be unchanged.";
             }
             enum stop-on-error {
               description
                 "The server will apply edits in the specified order
                  and will stop processing edits if any error occurs.
                  Any previous edits which were successfully applied
                  will remain applied.  No further edits will be
                  attempted after the first error is encountered.";
             }
             enum continue-on-error {
               description
                 "The server will apply edits in the specified order
                  and will continue processing edits if any error



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                  occurs.";
             }
           }
           default all-or-none;
           description
             "The error handling behavior for the ordered list of
              edits.";
         }

         list edit {
           key edit-id;

           description
             "Represents one edit within the YANG Patch
              request message.";

           leaf edit-id {
             type uint32;
             description
               "Arbitrary integer index for the edit.
                The server MUST process edits in ascending order.
                Error messages returned by the server pertaining
                to a specific edit will be identified by this
                identifier value.";
           }

           leaf operation {
             type enumeration {
               enum create {
                 description
                   "The target data node is created using the
                    supplied value, only if it does not already
                    exist.";
               }
               enum delete {
                 description
                   "Delete the target node, only if the data resource
                    currently exists, otherwise return an error.";
               }
               enum insert {
                 description
                   "Insert the supplied value into a user-ordered
                    list or leaf-list entry. The target node must
                    represent a new data resource.";
               }
               enum merge {
                 description
                   "The supplied value is merged with the target data



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                    node.";
               }
               enum move {
                 description
                   "Move the target node. Reorder a user-ordered
                    list or leaf-list. The target node must represent
                    an existing data resource.";
               }
               enum replace {
                 description
                   "The supplied value is used to replace the target
                    data node.";
               }
               enum remove {
                 description
                   "Delete the target node if it currently exists.";
               }
             }
             mandatory true;
             description
               "The datastore operation requested for the associated
                edit entry";
           }

           leaf target {
             type data-resource-identifier;
             mandatory true;
             description
               "Identifies the target data resource for the edit
                operation.";
           }

           leaf point {
             when "(../operation = 'insert' or " +
               "../operation = 'move') and " +
               "(../where = 'before' or ../where = 'after')" {
               description
                 "Point leaf only applies for insert or move
                  operations, before or after an existing entry.";
             }
             type data-resource-identifier;
             description
               "The absolute URL path for the data node that is being
                used as the insertion point or move point for the
                target of this edit entry.";
           }

           leaf where {



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             when "../operation = 'insert' or ../operation = 'move'" {
               description
                 "Where leaf only applies for insert or move
                  operations.";
             }
             type enumeration {
               enum before {
                 description
                   "Insert or move a data node before the data resource
                    identified by the 'point' parameter.";
               }
               enum after {
                 description
                   "Insert or move a data node after the data resource
                    identified by the 'point' parameter.";
               }
               enum first {
                 description
                   "Insert or move a data node so it becomes ordered
                    as the first entry.";
               }
               enum last {
                 description
                   "Insert or move a data node so it becomes ordered
                    as the last entry.";
               }

             }
             default last;
             description
               "Identifies where a data resource will be inserted or
                moved. YANG only allows these operations for
                list and leaf-list data nodes that are ordered-by
                user.";
           }

           anyxml value {
             when "(../operation = 'create' or " +
               "../operation = 'merge' " +
               "or ../operation = 'replace' or " +
               "../operation = 'insert')" {
               description
                 "Value node only used for create, merge,
                  replace, and insert operations";
             }
             description
               "Value used for this edit operation.";
           }



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         }
       }

     } // grouping yang-patch


     grouping yang-patch-status {

       description
         "A grouping that contains a YANG container
          representing the syntax and semantics of
          YANG Patch status response message.";

       container yang-patch-status {
         description
           "A container representing the response message
            sent by the server after a YANG Patch edit
            request message has been processed.";

         leaf patch-id {
           type string;
           description
             "The patch-id value used in the request";
         }

         container global-errors {
           uses errors;
           description
             "This container will be present if global
              errors unrelated to a specific edit occurred.";
         }

         container edit-status {
           description
             "This container will be present if there are
              edit-specific status responses to report.";

           list edit {
             key edit-id;

             description
               "Represents a list of status responses,
                corresponding to edits in the YANG Patch
                request message.";

             leaf edit-id {
               type uint32;
                description



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                  "Response status is for the edit list entry
                   with this edit-id value.";
             }
             choice edit-status-choice {
               description
                 "A choice between different types of status
                  responses for each edit entry.";

               leaf ok {
                 type empty;
                 description
                   "This edit entry was invoked without any
                    errors detected by the server associated
                    with this edit.";
               }
               leaf location {
                 type inet:uri;
                 description
                   "Contains the Location header value that would be
                    returned if this edit causes a new resource to be
                    created. If the edit identified by the same edit-id
                    value was successfully invoked and a new resource
                    was created, then this field will be returned
                    instead of 'ok'.";
               }
               leaf skipped {
                 type empty;
                 description
                   "This edit entry was skipped or not reached
                    by the server.";
               }
               case errors {
                 uses errors;
                 description
                   "The server detected errors associated with the
                     edit identified by the same edit-id value.";
               }
             }
           }
         }
       }
     }  // grouping yang-patch-status

     grouping errors {

       description
         "A grouping that contains a YANG container
          representing the syntax and semantics of a



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          YANG Patch errors report within a response message.";

       container errors {
         config false;  // needed so list error does not need a key
         description
           "Represents an error report returned by the server if
            a request results in an error.";

         list error {
           description
             "An entry containing information about one
              specific error that occurred while processing
              a RESTCONF request.";
           reference "RFC 6241, Section 4.3";

           leaf error-type {
             type enumeration {
               enum transport {
                 description "The transport layer";
               }
               enum rpc {
                 description "The rpc or notification layer";
               }
               enum protocol {
                 description "The protocol operation layer";
               }
               enum application {
                 description "The server application layer";
               }
             }
             mandatory true;
             description
               "The protocol layer where the error occurred.";
           }

           leaf error-tag {
             type string;
             mandatory true;
             description
               "The enumerated error tag.";
           }

           leaf error-app-tag {
             type string;
             description
               "The application-specific error tag.";
           }




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           leaf error-path {
             type data-resource-identifier;
             description
               "The target data resource identifier associated
                with the error, if any.";
           }

           leaf error-message {
             type string;
             description
               "A message describing the error.";
           }

           container error-info {
              description
                "A container allowing additional information
                 to be included in the error report.";
              // arbitrary anyxml content here
           }
         }
       }
     } // grouping errors


     grouping restconf {

       description
         "A grouping that contains a YANG container
          representing the syntax and semantics of
          the RESTCONF API resource.";

       container restconf {
         description
           "Conceptual container representing the vnd.yang.api
            resource type.";

         container datastore {
           description
             "Container representing the vnd.yang.datastore resource
              type. Represents the conceptual root of the unified
              datastore containing YANG data nodes.  The child nodes
              of this container can be data resources (vnd.yang.data)
              defined as top-level YANG data nodes from the modules
              advertised by the server in /restconf/modules.";
         }
         container modules {
           description
             "Contains a list of module description entries.



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              These modules are currently loaded into the server.";

           list module {
             key "name revision";
             description
               "Each entry represents one module currently
                supported by the server.";

             leaf name {
               type string;
               description "The YANG module name.";
             }
             leaf revision {
               type union {
                 type yang:date-and-time;
                 type string { length 0; }
               }
               description
                 "The YANG module revision date. An empty string is
                  used if no revision statement is present in the
                  YANG module.";
             }
             leaf namespace {
               type inet:uri;
               mandatory true;
               description
                 "The XML namespace identifier for this module.";
             }
             leaf-list feature {
               type string;
               description
                 "List of YANG feature names from this module that are
                  supported by the server.";
             }
             leaf-list deviation {
               type string;
               description
                 "List of YANG deviation module names used by this
                  server to modify the conformance of the module
                  associated with this entry.";
             }
           }
         }
         container operations {
           description
             "Container for all operation resources
              (vnd.yang.operation),




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              Each resource is represented as an empty leaf with the
              name of the RPC operation from the YANG rpc statement.

              E.g.;

                 POST /restconf/operations/show-log-errors

                 leaf show-log-errors {
                   type empty;
                 }
             ";
         }
         leaf version {
           type enumeration {
             enum "1.0" {
               description
                 "Version 1.0 of the RESTCONF protocol.";
             }
           }
           config false;
           description
             "Contains the RESTCONF protocol version.";
         }
       }
     }  // grouping restconf

   }



   <CODE ENDS>




















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9.  IANA Considerations

9.1.  Well-Known URI

   This memo registers the 'restconf' well-known URI in the Well-Known
   URIs registry as defined by [RFC5785].

      URI suffix: restconf

      Change controller: IETF

      Specification document(s): RFC XXXX

      Related information: None

9.2.  YANG Module Registry

   This document registers one URI in the IETF XML registry [RFC3688].
   Following the format in RFC 3688, the following registration is
   requested to be made.

        // RFC Ed.: replace XXXX with 'ietf' and remove this note
        URI: urn:XXXX:params:xml:ns:yang:ietf-restconf
        Registrant Contact: The NETMOD WG of the IETF.
        XML: N/A, the requested URI is an XML namespace.

   This document registers one YANG module in the YANG Module Names
   registry [RFC6020].

     name:         ietf-restconf
     namespace:    urn:ietf:params:xml:ns:yang:ietf-restconf
     prefix:       restconf
     // RFC Ed.: replace XXXX with RFC number and remove this note
     reference:    RFC XXXX

















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10.  Security Considerations

   TBD
















































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11.  Change Log

       -- RFC Ed.: remove this section before publication.

11.1.  YANG-API-01 to RESTCONF-00

   o  Protocol renamed from YANG-API to RESTCONF

   o  Fields are clarified.  Containers and lists are sub-resources.
      All other YANG data node types are fields within a parent
      resource.

   o  The 'optional-key' YANG extension has been removed.

   o  The default value is returned by the server if the target resource
      represents a missing data node but the server is using a default
      value for the leaf.

   o  The default for the 'depth' parameter has been changed from '1' to
      'unbounded'.  The depth is only limited if an integer value for
      this parameter is specified by the client.

   o  The default for the 'format' parameter has been changed from
      'json' to 'xml'.

   o  expanded introduction

   o  removed transactions

   o  removed capabilities

   o  removed usage of Range and IfRange headers

   o  simplified editing model

   o  removed global protocol operations from ietf-restconf.yang

   o  changed RPC operation terminology to protocol operation

   o  updated JSON draft reference

   o  updated open issues section

   o  updated IANA section

   o  added YANG Patch





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   o  added YANG definitions to ietf-restconf.yang

   o  added Kent Watsen and Rex Fernando as co-authors

   o  updated YANG modules so they pass pyang --ietf checking

   o  changed examples so resource URIs use the module name variant to
      identify data resources

   o  changed depth behavior so the entire server contents are not
      returned for "GET /.well-known/restconf"; Server will stop at new
      resource type; e.g. yang.api --> yang.dataastore returns the
      datastore as an empty node; yang.api --> yang.operation returns
      the operation name as an empty node;





































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12.  Closed Issues

   o  Which WG should do this work?  NETCONF?  NETMOD?  It is not clear
      since RESTCONF builds on concepts and standards from documents
      owned by both working groups.

   A: The NETCONF WG would do this work.

   o  Should sessions be used or not?  Should "reusable sessions" be
      used?  Better for auditing?  How does locking of the /.well-known/
      restconf/datastore resource work for multiple edits if a session
      is 1 operation?  When does the server release the lock and decide
      it has been abandoned or client was disconnected?

   A: RESTCONF is a session-less protocol.  It could be implemented to
   utilize persistent HTTP connections, but this is not required or
   designed into the protocol.

   o  Should the "/.well-known/restconf/modules" resource within the API
      resource be a separate resource, with its own timestamp?
      Currently the API timestamp is coupled to any changes to the list
      of loaded modules.  Should the API resource be static and
      cacheable?

   A: all child containers are considered sub-resources.  The server MAY
   support timestamps and entity IDs for data nodes.

   o  What to do about no REMOVE operation, just DELETE?  The effect is
      local to the request; in a NETCONF edit-config it is worse, since
      the netconf request might create/delete/modify many nodes

   A: The YANG Patch operation allows remove or delete semantics.

   o  Should every YANG data node be a data resource and every YANG RPC
      statement an operation resource?  Is a YANG extension needed to
      allow data modeler control of resource boundaries?

   A: Nested containers and lists are considered sub-resources.
   Terminal nodes (leaf, leaf-list, anyxml) are considered properties of
   the parent resource.

   o  Resource creation order and other dependencies between resources
      are not well identified in YANG.  YANG has leafrefs and instance-
      identifiers, which can be used to identify some order
      dependencies.  Are any new mechanisms needed in RESTCONF needed to
      identify resource creation order and other dependency
      requirements?




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   A: YANG Patch allows the client to control creation order when
   multiple resources need to be edited at once.  The edit operations
   allow the server to order all the descendant resources provided by
   the client, for a single datastore edit target node.

   o  Encoding of leafrefs?  Is there some additional meta-data needed?
      Do leafref nodes need to be identified in responses (RFC 5988) or
      is the YANG module definition sufficient to provide this meta-
      data?

   A: no special message encoding of leaf-refs is needed.  The server
   must understand the YANG schema no matter what protocol or encoding
   is used.

   o  What should the default algorithm be for defining data resources?
      Should the default for an augment from another namespace be to
      start a new resource?  Top-level data node defaults as a resource
      OK?

   A: Augmented nodes do not follow different rules than other nested
   YANG structures.  Containers and lists start new sub-resources.






























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13.  Open Issues

   o  There is no "message-id" field in a RESTCONF message.  Is a
      message identifier needed?  If so, should either the "Message-ID"
      or "Content-ID" header from RFC 2392 be used for this purpose?

   o  What syntax should be used for the "select" query parameter?  The
      current choices are "xpath" and "path-expr".  Perhaps an
      additional parameter to identify the select string format is
      needed to allow extensibility?

   o  Are all header lines used by RESTCONF supported by common
      application frameworks, such as FastCGI and WSGI?  If not, then
      should query parameters be used instead, since the QUERY_STRING is
      widely available to WEB applications?

   o  Should the <errors> element returned in error responses be a
      separate media type?

   o  How should additional datastores be supported, which may be added
      to the NETCONF/NETMOD framework in the future?

   o  How does a client know which PATCH media types are supported by
      the server in addition to application/vnd.yang.data and
      application/vnd.yang.patch?

   o  Is the /.well-known/restconf/version field considered meta-data?
      Should it be returned as XRD (Extensible Resource Descriptor)?  In
      addition or instead of the version field?  Should this be the
      ietf-restconf YANG module revision date, instead of the string
      1.0?

   o  Notification message delivery is TBD

   o  Alignment between NETCONF and RESTCONF notification is expected to
      be very close to RFC 5277 design.  Additional Sub/pub features
      still TBD.

   o  Some sections may need to be rewritten to support notifications
      and event resources

   o  Since data resources can only be YANG containers or lists, what
      should be done about top-level YANG data nodes that are not
      containers or lists?  Are they allowed in RESTCONF?

   o  Can a choice be a resource?  YANG choices are invisible to
      RESTCONF at this time.




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14.  Example YANG Module

   module example-jukebox {

      namespace "http://example.com/ns/example-jukebox";
      prefix "jbox";

      organization "Example, Inc.";
      contact "support at example.com";
      description "Example Jukebox Data Model Module";
      revision "2013-09-04" {
        description "Initial version.";
        reference "example.com document 1-4673";
      }

      identity genre {
        description "Base for all genre types";
      }

      // abbreviated list of genre classifications
      identity Alternative {
        base genre;
        description "Alternative music";
      }
      identity Blues {
        base genre;
        description "Blues music";
      }
      identity Country {
        base genre;
        description "Country music";
      }
      identity Jazz {
        base genre;
        description "Jazz music";
      }
      identity Pop {
        base genre;
        description "Pop music";
      }
      identity Rock {
        base genre;
        description "Rock music";
      }

      container jukebox {
        presence
          "An empty container indicates that the jukebox



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           service is available";

        description
          "Represents a jukebox resource, with a library, playlists,
           and a plaay operation.";

        container library {

          description "Represents the jukebox library resource.";

          list artist {
            key name;

            description
              "Represents one artist resource within the
               jukebox library resource.";

            leaf name {
              type string {
                length "1 .. max";
              }
              description "The name of the artist.";
            }

            list album {
              key name;

              description
                "Represents one album resource within one
                 artist resource, within the jukebox library.";

              leaf name {
                type string {
                  length "1 .. max";
                }
                description "The name of the album.";
              }

              leaf genre {
                type identityref { base genre; }
                description
                  "The genre identifying the type of music on
                   the album.";
              }

              leaf year {
                type uint16 {
                  range "1900 .. max";



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                }
                description "The year the album was released";
              }

              list song {
                key name;

                description
                  "Represents one song resource within one
                   album resource, within the jukebox library.";

                leaf name {
                  type string {
                     length "1 .. max";
                  }
                  description "The name of the song";
                }
                leaf location {
                  type string;
                  mandatory true;
                  description
                   "The file location string of the
                    media file for the song";
                }
                leaf format {
                  type string;
                  description
                    "An identifier string for the media type
                     for the file associated with the
                     'location' leaf for this entry.";
                }
                leaf length {
                  type uint32;
                  units "seconds";
                  description
                    "The duration of this song in seconds.";
                }
              }   // end list 'song'
            }   // end list 'album'
          }  // end list 'artist'

          leaf artist-count {
             type uint32;
             units "songs";
             config false;
             description "Number of artists in the library";
          }
          leaf album-count {



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             type uint32;
             units "albums";
             config false;
             description "Number of albums in the library";
          }
          leaf song-count {
             type uint32;
             units "songs";
             description "Number of songs in the library";
          }
        }  // end library

        list playlist {
          key name;

          description
            "Example configuration data resource";

          leaf name {
            type string;
            description
              "The name of the playlist.";
          }
          leaf description {
            type string;
            description
              "A comment describing the playlist.";
          }
          list song {
            key index;
            ordered-by user;

            description
              "Example nested configuration data resource";

            leaf index {    // not really needed
              type uint32;
              description
                "An arbitrary integer index for this
                 playlist song.";
            }
            leaf id {
              type instance-identifier;
              mandatory true;
              description
                "Song identifier. Must identify an instance of
                 /jukebox/library/artist/album/song/name.";
            }



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          }
        }

        container player {
          description
            "Represents the jukebox player resource.";

          leaf gap {
            type decimal64 {
              fraction-digits 1;
              range "0.0 .. 2.0";
            }
            units "tenths of seconds";
            description "Time gap between each song";
          }
        }
      }

      rpc play {
        description "Control function for the jukebox player";
        input {
          leaf playlist {
            type string;
            mandatory true;
            description "playlist name";
          }
          leaf song-number {
            type uint32;
            mandatory true;
            description "Song number in playlist to play";
          }
        }
      }
   }

















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15.  References

15.1.  Normative References

   [I-D.lhotka-netmod-json]
              Lhotka, L., "Modeling JSON Text with YANG",
              draft-lhotka-netmod-yang-json-01 (work in progress),
              April 2013.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              January 2004.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              April 2010.

   [RFC5789]  Dusseault, L. and J. Snell, "PATCH Method for HTTP",
              RFC 5789, March 2010.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, June 2011.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              March 2012.

   [RFC6991]  Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
              July 2013.







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15.2.  Informative References

   [RFC6902]  Bryan, P. and M. Nottingham, "JavaScript Object Notation
              (JSON) Patch", RFC 6902, April 2013.















































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Authors' Addresses

   Andy Bierman
   YumaWorks

   Email: andy@yumaworks.com


   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com


   Kent Watsen
   Juniper Networks

   Email: kwatsen@juniper.net


   Rex Fernando
   Cisco

   Email: rex@cisco.com



























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