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Versions: 00 01 02 03 04 draft-ietf-netconf-restconf

Network Working Group                                         A. Bierman
Internet-Draft                                                 YumaWorks
Intended status: Standards Track                            M. Bjorklund
Expires: April 22, 2014                                   Tail-f Systems
                                                               K. Watsen
                                                        Juniper Networks
                                                             R. Fernando
                                                                   Cisco
                                                        October 19, 2013


                           RESTCONF Protocol
                   draft-bierman-netconf-restconf-02

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 April 22, 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
       1.3.5.  Tree Diagrams . . . . . . . . . . . . . . . . . . . .  10
     1.4.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  11
       1.4.1.  Resource URI Map  . . . . . . . . . . . . . . . . . .  11
       1.4.2.  RESTCONF Message Examples . . . . . . . . . . . . . .  12
   2.  Framework . . . . . . . . . . . . . . . . . . . . . . . . . .  20
     2.1.  Message Model . . . . . . . . . . . . . . . . . . . . . .  20
     2.2.  Notification Model  . . . . . . . . . . . . . . . . . . .  20
       2.2.1.  Server Support  . . . . . . . . . . . . . . . . . . .  20
       2.2.2.  Event Stream Discovery  . . . . . . . . . . . . . . .  20
       2.2.3.  Subscribing to Receive Notifications  . . . . . . . .  21
       2.2.4.  Receiving Event Notifications . . . . . . . . . . . .  24
     2.3.  Resource Model  . . . . . . . . . . . . . . . . . . . . .  25
       2.3.1.  RESTCONF Resource Types . . . . . . . . . . . . . . .  26
       2.3.2.  Resource Discovery  . . . . . . . . . . . . . . . . .  26
     2.4.  Datastore Model . . . . . . . . . . . . . . . . . . . . .  27
       2.4.1.  Content Model . . . . . . . . . . . . . . . . . . . .  27
       2.4.2.  Editing Model . . . . . . . . . . . . . . . . . . . .  28
       2.4.3.  Locking Model . . . . . . . . . . . . . . . . . . . .  29
       2.4.4.  Persistence Model . . . . . . . . . . . . . . . . . .  29
       2.4.5.  Defaults Model  . . . . . . . . . . . . . . . . . . .  29
     2.5.  Transaction Model . . . . . . . . . . . . . . . . . . . .  30
     2.6.  Extensibility Model . . . . . . . . . . . . . . . . . . .  30
     2.7.  Versioning Model  . . . . . . . . . . . . . . . . . . . .  30
     2.8.  Retrieval Filtering Model . . . . . . . . . . . . . . . .  31
     2.9.  Access Control Model  . . . . . . . . . . . . . . . . . .  31
   3.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .  32
     3.1.  OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . .  32
     3.2.  HEAD  . . . . . . . . . . . . . . . . . . . . . . . . . .  34
     3.3.  GET . . . . . . . . . . . . . . . . . . . . . . . . . . .  34
     3.4.  POST  . . . . . . . . . . . . . . . . . . . . . . . . . .  36
       3.4.1.  Create Resource Mode  . . . . . . . . . . . . . . . .  36
       3.4.2.  Invoke Operation Mode . . . . . . . . . . . . . . . .  37
     3.5.  PUT . . . . . . . . . . . . . . . . . . . . . . . . . . .  37



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     3.6.  PATCH . . . . . . . . . . . . . . . . . . . . . . . . . .  38
     3.7.  DELETE  . . . . . . . . . . . . . . . . . . . . . . . . .  38
     3.8.  Query Parameters  . . . . . . . . . . . . . . . . . . . .  38
       3.8.1.  "depth" Parameter . . . . . . . . . . . . . . . . . .  39
       3.8.2.  "format" Parameter  . . . . . . . . . . . . . . . . .  41
       3.8.3.  "insert" Parameter  . . . . . . . . . . . . . . . . .  42
       3.8.4.  "point" Parameter . . . . . . . . . . . . . . . . . .  43
       3.8.5.  "select" Parameter  . . . . . . . . . . . . . . . . .  44
     3.9.  Protocol Operations . . . . . . . . . . . . . . . . . . .  45
   4.  Messages  . . . . . . . . . . . . . . . . . . . . . . . . . .  46
     4.1.  Request URI Structure . . . . . . . . . . . . . . . . . .  46
     4.2.  Message Headers . . . . . . . . . . . . . . . . . . . . .  47
     4.3.  Message Encoding  . . . . . . . . . . . . . . . . . . . .  48
     4.4.  RESTCONF Meta-Data  . . . . . . . . . . . . . . . . . . .  48
       4.4.1.  JSON Encoding of RESTCONF Meta-Data . . . . . . . . .  49
     4.5.  Return Status . . . . . . . . . . . . . . . . . . . . . .  51
     4.6.  Message Caching . . . . . . . . . . . . . . . . . . . . .  51
   5.  Resources . . . . . . . . . . . . . . . . . . . . . . . . . .  52
     5.1.  API Resource (/restconf)  . . . . . . . . . . . . . . . .  52
       5.1.1.  /restconf/config  . . . . . . . . . . . . . . . . . .  53
       5.1.2.  /restconf/operational . . . . . . . . . . . . . . . .  53
       5.1.3.  /restconf/modules . . . . . . . . . . . . . . . . . .  54
       5.1.4.  /restconf/operations  . . . . . . . . . . . . . . . .  56
       5.1.5.  /restconf/streams . . . . . . . . . . . . . . . . . .  56
     5.2.  Datastore Resource  . . . . . . . . . . . . . . . . . . .  56
     5.3.  Data Resource . . . . . . . . . . . . . . . . . . . . . .  57
       5.3.1.  Encoding YANG Instance Identifiers in the Request
               URI . . . . . . . . . . . . . . . . . . . . . . . . .  57
       5.3.2.  Data Resource Retrieval . . . . . . . . . . . . . . .  60
     5.4.  Operation Resource  . . . . . . . . . . . . . . . . . . .  61
       5.4.1.  Encoding Operation Input Parameters . . . . . . . . .  61
       5.4.2.  Encoding Operation Output Parameters  . . . . . . . .  62
     5.5.  Stream Resource . . . . . . . . . . . . . . . . . . . . .  63
   6.  Error Reporting . . . . . . . . . . . . . . . . . . . . . . .  64
     6.1.  Error Response Message  . . . . . . . . . . . . . . . . .  65
   7.  YANG Patch  . . . . . . . . . . . . . . . . . . . . . . . . .  67
     7.1.  Why not use JSON Patch? . . . . . . . . . . . . . . . . .  68
     7.2.  YANG Patch Target Data Node . . . . . . . . . . . . . . .  69
     7.3.  YANG Patch Edit Operations  . . . . . . . . . . . . . . .  69
     7.4.  YANG Patch Error Handling . . . . . . . . . . . . . . . .  69
     7.5.  YANG Patch Response . . . . . . . . . . . . . . . . . . .  70
     7.6.  YANG Patch Examples . . . . . . . . . . . . . . . . . . .  70
       7.6.1.  Add Resources: Error  . . . . . . . . . . . . . . . .  70
       7.6.2.  Add Resources: Success  . . . . . . . . . . . . . . .  72
       7.6.3.  Move list entry example . . . . . . . . . . . . . . .  74
   8.  RESTCONF module . . . . . . . . . . . . . . . . . . . . . . .  76
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  91
     9.1.  YANG Module Registry  . . . . . . . . . . . . . . . . . .  91



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     9.2.  application/yang Media Type . . . . . . . . . . . . . . .  91
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  92
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  93
     11.1. Normative References  . . . . . . . . . . . . . . . . . .  93
     11.2. Informative References  . . . . . . . . . . . . . . . . .  94
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  95
     A.1.  01 to 02  . . . . . . . . . . . . . . . . . . . . . . . .  95
     A.2.  00 to 01  . . . . . . . . . . . . . . . . . . . . . . . .  95
     A.3.  YANG-API-01 to RESTCONF-00  . . . . . . . . . . . . . . .  96
   Appendix B.  Closed Issues  . . . . . . . . . . . . . . . . . . .  98
   Appendix C.  Open Issues  . . . . . . . . . . . . . . . . . . . . 100
     C.1.  message-id  . . . . . . . . . . . . . . . . . . . . . . . 100
     C.2.  select parameter  . . . . . . . . . . . . . . . . . . . . 100
     C.3.  server support verification . . . . . . . . . . . . . . . 100
     C.4.  error media type  . . . . . . . . . . . . . . . . . . . . 100
     C.5.  additional datastores . . . . . . . . . . . . . . . . . . 100
     C.6.  PATCH media type discovery  . . . . . . . . . . . . . . . 100
     C.7.  RESTCONF version  . . . . . . . . . . . . . . . . . . . . 100
     C.8.  YANG to resource mapping  . . . . . . . . . . . . . . . . 101
     C.9.  .well-known usage . . . . . . . . . . . . . . . . . . . . 101
     C.10. _self links for HATEOAS support . . . . . . . . . . . . . 102
     C.11. netconf-state monitoring support  . . . . . . . . . . . . 102
     C.12. secure transport  . . . . . . . . . . . . . . . . . . . . 102
   Appendix D.  Example YANG Module  . . . . . . . . . . . . . . . . 103
     D.1.  example-jukebox YANG Module . . . . . . . . . . . . . . . 103
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 109

























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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.

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, but it 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

   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 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
   modeling language to define the application-specific content of the
   API.  The client would discover each new child resource as it
   traverses the URIs returned as Location IDs to discover the server
   capabilities.

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

   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.



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   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.

   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

   o  datastore

   o  configuration datastore

   o  protocol operation





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   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

   o  leaf

   o  leaf-list

   o  list




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   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/
      yang.api+xml" or "application/yang.api+json".  API resources can
      only be edited by the server.

   o  data resource: a resource with the media type "application/
      yang.data+xml" or "application/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/
      yang.datastore+xml" or "application/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 stream resource: a resource with the media type
      "application/yang.stream+xml" or "application/yang.stream+json".
      This resource represents an SSE event stream.  The content
      consists of text using the media type "text/event-stream".  Each
      event represents one <notification> message generated by the
      server.  It contains a conceptual system or data-model specific
      event that is delivered within a notification event stream.

   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.

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




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

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

   o  query parameter: a parameter (and its value if any), encoded
      within the query component 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/yang.patch+xml" or "application/yang.patch+json".

   o  YANG Patch Status: the status data returned for a YANG Patch
      operation identified by the media type "application/
      yang.patch-status+xml" or "application/yang.patch-status+json".

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

1.3.5.  Tree Diagrams

   A simplified graphical representation of the data model is used in
   this document.  The meaning of the symbols in these diagrams is as
   follows:

   o  Brackets "[" and "]" enclose list keys.

   o  Abbreviations before data node names: "rw" means configuration
      (read-write) and "ro" state data (read-only).

   o  Symbols after data node names: "?" means an optional node and "*"
      denotes a "list" and "leaf-list".




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   o  Parentheses enclose choice and case nodes, and case nodes are also
      marked with a colon (":").

   o  Ellipsis ("...") stands for contents of subtrees that are not
      shown.

1.4.  Overview

   This document defines the RESTCONF protocol, a RESTful API for
   accessing conceptual datastores containing data defined with the 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, top-level
   data node resources, and notification event messages supported by the
   server.

1.4.1.  Resource URI Map

   The URI hierarchy for the RESTCONF resources consists of an entry
   point container, 4 top-level resources, and 1 field.  Refer to
   Section 5 for details on each URI.

     /restconf
        /config
           /<top-level-data-nodes> (configuration data)
        /operational
           /<top-level-data-nodes> (operational data)
        /modules
           /module
              /name
              /revision
              /namespace
              /feature
              /deviation
        /operations
           /<custom protocol operations>
        /streams
           /stream
              /name
              /description
              /replay-support
              /replay-log-creation-time
              /events
        /version (field)




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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 Appendix D.1.

   This section shows some typical RESTCONF message exchanges.

1.4.2.1.  Retrieve the Top-level API Resource

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

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

      {
        "ietf-restconf:restconf": {
          "config" : [ null ],
          "operational" : [ null ],
          "modules": {
            "module": [
              {
                "name" : "example-jukebox",
                "revision" : "2013-10-19",
                "namespace" : "http://example.com/ns/example-jukebox"
              }
            ]
          },
          "operations" : {
             "play" : [ null ]
          },
          "streams" : {
            "stream" : [
              {
                "name" : "NETCONF",
                "description" : "default NETCONF event stream",
                "replay-support" : true,
                "replay-log-creation-time:" : "2007-07-08T00:00:00Z",
                "events" : [ 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 /restconf HTTP/1.1
      Host: example.com
      Accept: application/yang.api+xml

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

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



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   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/yang.api+xml


      <restconf xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
        <config/>
        <operational/>
        <modules>
          <module>
            <name>example-jukebox</name>
            <revision>2013-10-19</revision>
            <namespace>
              http://example.com/ns/example-jukebox
            </namespace>
          </module>
        </modules>
        <operations>
          <play xmlns="http://example.com/ns/example-jukebox"/>
        </operations>
        <streams>
          <stream>
            <name>NETCONF</name>
            <description>default NETCONF event stream
            </description>
            <replay-support>true</replay-support>
            <replay-log-creation-time>
               2007-07-08T00:00:00Z
            </replay-log-creation-time>
            <events/>
          </stream>
        </streams>
        <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:





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      POST /restconf/config HTTP/1.1
      Host: example.com
      Content-Type: application/yang.data+json

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

   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 17:01:00 GMT
      Server: example-server
      Location: http://example.com/restconf/config/
         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 /restconf/config/example-jukebox:jukebox/library HTTP/1.1
      Host: example.com
      Content-Type: application/yang.data+json

      { "example-jukebox:artist" : {
          "name" : "Foo Fighters"
        }
      }

   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/restconf/config/
           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:






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

      {
        "example-jukebox: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/restconf/config/
        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.

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:














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

      {
        "example-jukebox: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 /restconf/config/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
      Host: example.com
      If-Match: b8389233a4c
      Content-Type: application/yang.data+json

      { "example-jukebox:year" : 2011 }

   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:



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      PATCH /restconf/config/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light HTTP/1.1
      Host: example.com
      If-Match: b8389233a4c
      Content-Type: application/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 /restconf/config/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.

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

   The server might respond:





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      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,
   which allows multiple datastore edits within a single message.

2.2.  Notification Model

   The RESTCONF protocol supports YANG-defined event notifications.  The
   solution preserves aspects of NETCONF Event Notifications [RFC5277]
   while utilizing the Server-Sent Events [wd-eventsource] transport
   strategy.

2.2.1.  Server Support

   A RESTCONF server is not required to support RESTCONF notifications.
   Clients may determine if a server supports RESTCONF notifications by
   using the HTTP operation OPTIONS, HEAD, or GET on the "/restconf/
   streams" resource described below.  The server does not support
   RESTCONF notifications if an HTTP error code is returned (e.g. 404
   Not Found).

2.2.2.  Event Stream Discovery

   A RESTCONF client retrieves the list of supported event streams from
   a RESTCONF server using the GET operation on the "/restconf/streams"
   resource.

   The "/restconf/streams" container definition in the "ietf-restconf"
   module defined in Section 8 is used to specify the structure and
   syntax of the conceptual fields and sub-resources within the
   "streams" resource.

   For example:

      GET /restconf/streams HTTP/1.1
      Host: example.com
      Accept: application/yang.api+xml

   Available event streams for the requesting session are returned



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   according the YANG container [RFC5277]:

      HTTP/1.1 200 OK
      Content-Type: application/yang.api+xml


      <streams xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
         <stream>
            <name>NETCONF</name>
            <description>default NETCONF event stream
            </description>
            <replay-support>true</replay-support>
            <replay-log-creation-time>
               2007-07-08T00:00:00Z
            </replay-log-creation-time>
            <events/>
         </stream>
         <stream>
            <name>SNMP</name>
            <description>SNMP notifications</description>
            <replay-support>false</replay-support>
            <events/>
         </stream>
         <stream>
            <name>syslog-critical</name>
            <description>Critical and higher severity
            </description>
            <replay-support>true</replay-support>
            <replay-log-creation-time>
               2007-07-01T00:00:00Z
            </replay-log-creation-time>
            <events/>
         </stream>
      </streams>

2.2.3.  Subscribing to Receive Notifications

   RESTCONF clients can subscribe to receive notifications by sending an
   HTTP GET to the "/restconf/streams/stream/<stream-name>" resource
   with the "Accept" type "text/event-stream", which signals the desire
   to use the Server Sent Events [wd-eventsource] transport strategy.

   For example:

      GET /restconf/streams/stream/NETCONF/events HTTP/1.1
      Host: example.com
      Accept: text/event-stream
      Cache-Control: no-cache



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      Connection: keep-alive

   A RESTCONF client MAY request the server compress the events using
   the HTTP header field "Accept-Encoding".  For instance:

      GET /restconf/streams/stream/NETCONF/events HTTP/1.1
      Host: example.com
      Accept: text/event-stream
      Cache-Control: no-cache
      Connection: keep-alive
      Accept-Encoding: gzip, deflate

2.2.3.1.  Query Parameters

   Consistent with [RFC5277], RESTCONF notification subscriptions may
   specify parameters indicating the events it wishes to receive.  These
   parameters are passed in RESTCONF using HTTP query parameters as
   follows:

2.2.3.1.1.  start-time

   An optional parameter used to trigger the replay feature and indicate
   that the replay should start at the time specified.  If the stream
   does not support replay, per the "replay-support" attribute returned
   by the /restconf/streams resource, then the server MUST return the
   HTTP error code 400 Bad Request.  If the "start-time" parameter is
   not present, this is not a replay subscription.  It is not valid to
   specify start times that are later than the current time.  If the
   "start-time" specified is earlier than the log can support, the
   replay will begin with the earliest available notification.  This
   parameter is of YANG type "date-and-time" from the "ietf-inet-types"
   module in [RFC6991].

   Example: (line wrapped for display purposes only)

      GET /restconf/streams/stream/syslog-critical/events?
         start-time=2012-12-31T23:59:59Z

2.2.3.1.2.  stop-time

   The optional "stop-time" parameter is used with the optional replay
   feature to indicate the newest notifications of interest.  This
   parameter MUST be used with and have a value later than the
   "start-time" parameter.  If the "stop-time" parameter is not present,
   the notifications will continue until the subscription is terminated.
   Values of "stop-time" in the future are valid.  This parameter is of
   YANG type "date-and-time" from the "ietf-inet-types" module in
   [RFC6991].



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   Example: ('\' added for formatting only)

      GET /restconf/events?start-time=2013-12-31T23:59:00Z;\
      stop-time=2014-01-01T00:01:00Z

2.2.3.1.3.  filter

   The optional "filter" parameter is used to indicate which subset of
   all possible events are of interest.  If not present, all events not
   precluded by other parameters will be sent.  The format of this
   parameter is an XPath expression as defined in [XPATH].  The XPath
   filter expression is evaluated in the following context:

   o  The set of namespace declarations is the set of prefix and
      namespace pairs for all supported YANG modules, where the prefix
      is the YANG module name, and the namespace is as defined by the
      "namespace" statement in the YANG module.

   o  The function library is the core function library defined in
      [XPATH].

   o  The set of variable bindings is empty.

   o  The context node is the root node

   The filter is used as defined in [RFC5277], section 3.6.  If the
   boolean result of the expression is true when applied to the
   conceptual "notification" document root, then the notification event
   is delivered to the client.

   Examples: (lines wrapped for display purposes only)




















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      // filter = /event/eventClass='fault'
      GET /restconf/streams/stream/NETCONF/events?
         filter=%2Fevent%2FeventClass%3D'fault'

      // filter = /event/severityCode<=4
      GET /restconf/streams/stream/NETCONF/events?
         filter=%2Fevent%2FseverityCode%3C%3D4

      // filter = /linkUp|/linkDown
      GET /restconf/streams/stream/SNMP/events?
         filter=%2FlinkUp%7C%2FlinkDown

      // filter = /*/reportingEntity/card!='Ethernet0'
      GET /restconf/streams/stream/NETCONF/events?
         filter=%2F*%2FreportingEntity%2Fcard%21%3D'Ethernet0'

      // filter = /*/email-addr[contains(.,'company.com')]
      GET /restconf/streams/stream/critical-syslog/events?
         filter=%2F*%2Femail-addr[contains(.%2C'company.com')]

      // Note: the module name is used as prefix.
      // filter = (/example-mod:event1/name='joe' and
      //           /example-mod:event1/status='online')
      GET /restconf/streams/stream/NETCONF/events?
        filter=(%2Fexample-mod%3Aevent1%2Fname%3D'joe'%20and
                %20%2Fexample-mod%3Aevent1%2Fstatus%3D'online')

2.2.4.  Receiving Event Notifications

   RESTCONF notifications are encoded per NETCONF Event Notifications
   [RFC5277], though they may be in either XML or JSON format, depending
   on value of the "format" query parameter passed by the client.  The
   structure of the event data MUST conform to the "notification"
   element definition in section 4 of [RFC5277].

   An example SSE notification encoded using XML:

      data: <notification
      data:    xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
      data:    <event-time>2013-09-30T00:01:00Z</event-time>
      data:    <event xmlns="http://example.com/event/1.0">
      data:       <eventClass>fault</eventClass>
      data:       <reportingEntity>
      data:           <card>Ethernet0</card>
      data:       </reportingEntity>
      data:       <severity>major</severity>
      data:     </event>
      data: </notification>



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   An example SSE notification encoded using JSON:

      data: {
      data:   "ietf-restconf:notification": {
      data:     "eventTime": "2013-09-30T00:01:00Z",
      data:     "example-mod:event": {
      data:       "eventClass": "fault",
      data:       "reportingEntity": { "card": "Ethernet0" },
      data:       "severity": "major"
      data:     }
      data:   }
      data: }

   Alternatively, since neither XML nor JSON are whitespace sensitive,
   the above messages can be encoded onto a single line.  For example:

   XML: ('\' line wrapping added for formatting only)

      data: <notification xmlns="urn:ietf:params:xml:ns:yang:ietf-rest\
      conf"><event-time>2013-09-30T00:01:00Z</event-time><event xmlns="\
      http://example.com/event/1.0"><eventClass>fault</eventClass><repo\
      rtingEntity><card>Ethernet0</card></reportingEntity><severity>maj\
      or</severity></event></notification>

   JSON: ('\' line wrapping added for formatting only)

      data: { "ietf-restconf:notification": { "event-time": "2013-09-30\
      T00:01:00Z", "example-mod:event": { "eventClass": "fault", "repor\
      tingEntity": { "card": "Ethernet0" }, "severity": "major" } } }

   The SSE specifications supports the following additional fields:
   event, id and retry.  A RESTCONF server MAY send the "retry" field
   and, if it does, RESTCONF clients SHOULD use it.  A RESTCONF server
   SHOULD NOT send the "event" or "id" fields, as there are no
   meaningful values that could be used for them that would not be
   redundant to the contents of the notification itself.  RESTCONF
   servers that do not send the "id" field also do not need to support
   the HTTP header "Last-Event-Id".  RESTCONF servers that do send the
   "id" field MUST still support the "startTime" query parameter as the
   preferred means for a client to specify where to restart the event
   stream.

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.




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   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 in YANG modules.

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.

             +--------------+-------------------------------+
             | Resource     | Media Type                    |
             +--------------+-------------------------------+
             | API          | application/yang.api          |
             | Datastore    | application/yang.datastore    |
             | Data         | application/yang.data         |
             | Operation    | application/yang.operation    |
             | Patch        | application/yang.patch        |
             | Patch Status | application/yang.patch-status |
             | Stream       | application/yang.stream       |
             +--------------+-------------------------------+

                           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 "/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



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   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 3.8.1 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 unified 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.

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 under "/restconf/modules" 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 stream 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.





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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.

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

2.4.2.1.  Edit Operation Discovery

   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.

   The server MUST maintain these properties for datastore resources,
   and MAY maintain them 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":






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

      { "example-jukebox: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/1.1 412 Precondition Failed
      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 model for handling default values 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.



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   If the target of a GET method (plus "select" value) is a data node
   that represents a container or list that has any fields with default
   values, for the fields that have not been given value yet, the server
   MAY return the default values that are in use by the server.

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

2.5.  Transaction Model

   The RESTCONF protocol provides 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 PATCH
   method using a new media type (application/yang.patch).  This allows
   a full 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, after one or more edit operations have been
   done.

   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.

   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





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   o  data and operation resource definition versions

   The protocol version is identified by the string used for the well-
   known URI entry point "/restconf".  This would be changed (e.g.,
   "/restconf2") if non-backward compatible changes are ever needed.
   Version changes that do not break backward-compatibility will not
   cause the entry point to change.

   The field "/restconf/version" in the API resource can be used by the
   client to identify the exact version of the RESTCONF protocol
   implemented by the server.

   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 the numeric string defined by the "/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 granular access control for operation
   and data resources using the NETCONF Access Control Model (NACM)
   [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" or <any>) |
         | 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.  The PATCH method is equivalent to a "merge" operation for a
   plain PATCH method (using the media type "application/yang.data").
   Any operation is possible within a YANG Patch (using the media type
   "application/yang.patch").

   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:



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

      OPTIONS /restconf/config/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 /restconf/operational/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 /restconf/operations/example-jukebox: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







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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.

   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 /restconf/config/example-jukebox:jukebox/library HTTP/1.1
      Host: example.com
      Accept: application/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/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:





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   +--------+---------+------------------------------------------------+
   | Name   | Section | Description                                    |
   +--------+---------+------------------------------------------------+
   | depth  | 3.8.1   | Control the depth of a retrieval request       |
   | format | 3.8.2   | Request either JSON or XML content in the      |
   |        |         | response                                       |
   | select | 3.8.5   | 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 /restconf/config/example-jukebox:jukebox/
        library/artist/Foo%20Fighters/album?format=json HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json

   The server might respond:

















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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:02:40 GMT
      Server: example-server
      Content-Type: application/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
        }
      }

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.







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      +--------+---------+-----------------------------------------+
      | Name   | Section | Description                             |
      +--------+---------+-----------------------------------------+
      | insert | 3.8.3   | Specify where to insert a resource      |
      | point  | 3.8.4   | 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.

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
   resource instance does not exist, the server MAY create it.

   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.



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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/
      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/
      yang.patch", then the PATCH method is a YANG Patch formatted list
      of edits (see Section 7).  The message body contains the XML 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 resource
   instance does not exist, the server MUST NOT create it.

   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



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   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.  "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 /restconf/config/example-jukebox:jukebox
         ?depth=2 HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json

   The server might respond:



















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      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/yang.data+json

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

   By default, the server will include all sub-resources within a
   retrieved resource, which have the same resource type as the
   requested resource.  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/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 are also returned as empty nodes (e.g. "play"
   operation).

   Request URL:

      GET /restconf HTTP/1.1

   Response:














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      {
        "ietf-restconf:restconf": {
          "config" : [ null ],
          "operational" : [ null ],
          "modules": {
            "module": [
              {
                "name" : "example-jukebox",
                "revision" : "2013-10-19",
                "namespace" : "http://example.com/ns/example-jukebox"
              }
            ]
          },
          "operations" : {
             "play" : [ null ]
          },
          "version": "1.0"
        }
      }

3.8.2.  "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 /restconf/config/example-routing:routing  HTTP/1.1
      Host: example.com
      Accept: application/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 /restconf/config/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.

3.8.3.  "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:

      POST /restconf/config/example-jukebox:jukebox/
        playlist/Foo-One?insert=first HTTP/1.1
      Host: example.com
      Content-Type: application/yang.data+json

      {
        "example-jukebox: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/restconf/config/
         example-jukebox:jukebox/playlist/Foo-One/song/1
      ETag: eeeada438af

3.8.4.  "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.

   Note that the first path component encoded for an instance identifier
   is the top-level YANG data node.  The "/restconf/config" entry point
   is not included in an instance-identifier.

      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 /restconf/config/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light?
         insert=after&point=%2Fexample-jukebox%3Ajukebox%2F
         library%2Fartist%2FFoo%20Fighters%2Falbum%2F
         Wasting%20Light%2Fsong%2FBridge%20Burning   HTTP/1.1
      Host: example.com
      Content-Type: application/yang.data+json

      {
        "example-jukebox: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

3.8.5.  "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 /restconf?select=version&format=json HTTP/1.1
      Host: example.com
      Accept: application/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/yang.api+json

      { "ietf-restconf: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/
   yang.operation+xml" or "application/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> /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 ("/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/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.
      The contents of the any query parameter value MUST be encoded
      according to [RFC2396], section 3.4.  Any reserved characters MUST
      be encoded with escape sequences, according to [RFC2396], section
      2.4.




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

   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             |
   | Cache-Control | The cache control parameters for the response     |
   | 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



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   defined in the YANG schema because it applies to the datastore, and
   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:


















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      Meta-data:

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

      YANG module: example
      YANG example:

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

   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 /restconf/config/example:top HTTP/1.1
      Host: example.com
      Accept: application/yang.data+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/yang.data+json

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





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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.

   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 the "If-None-Match"
   and/or "If-Modified-Since" headers, 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 (/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/yang.api+xml" or "application/yang.api+json".  It
   is accessible through the well-known relative URI "/restconf".

   YANG Tree Diagram for "application/yang.api" Resource Type:

      +--rw restconf
      |  +--rw config
      |  +--rw operational
      |  +--rw modules
      |  |  +--rw module [name revision]
      |  |     +--rw name         yang:yang-identifier
      |  |     +--rw revision     union
      |  |     +--rw namespace    inet:uri
      |  |     +--rw feature*     yang:yang-identifier
      |  |     +--rw deviation*   yang:yang-identifier
      |  +--rw operations
      |  +--rw streams
      |  |  +--rw stream [name]
      |  |     +--rw name                        string
      |  |     +--rw description?                string
      |  |     +--rw replay-support?             boolean
      |  |     +--rw replay-log-creation-time?   yang:date-and-time
      |  |     +--rw events?                     empty
      |  +--ro version?      enumeration
      +--rw notification
         +--rw event-time    yang:date-and-time

   The "restconf" container definition in the "ietf-restconf" module
   defined in Section 8 is used to specify the structure and syntax of
   the conceptual fields and sub-resources within the API resource.

   The "restconf" entry point container, and all fields and sub-
   resources with the same resource type, are defined in the namespace
   of the "ietf-restconf" module.

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




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   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 |
            | streams        | Notification event streams     |
            +----------------+--------------------------------+

                            RESTCONF Resources

5.1.1.  /restconf/config

   This mandatory resource represents the running configuration
   datastore.  It contains configuration data resources that may be
   retrieved and edited by a client.  It cannot be created or deleted by
   a client.  This resource type is defined in Section 5.2.

5.1.2.  /restconf/operational

   This mandatory resource represents the operational datastore.  It
   contains operational data and statistics data resources that may be
   retrieved by a client.  It cannot be created or deleted by the
   client.  This resource type is defined in Section 5.2.

   Example:

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

      GET /restconf/operational/example-jukebox:jukebox/library
         HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json




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   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/yang.data+json

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

5.1.3.  /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.

5.1.3.1.  /restconf/modules/module

   This mandatory resource contains one list entry 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" resource 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



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   retrieved with the GET or HEAD methods.  If not supported then the
   timestamp for the parent "modules" resource MAY be used instead.

5.1.3.2.  Retrieval Example

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

      GET /restconf/modules&format=json HTTP/1.1
      Host: example.com
      Accept: application/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/yang.api+json

      {
        "ietf-restconf: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" ]
            }
          ]
        }
      }






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5.1.4.  /restconf/operations

   This optional resource is a container that 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.

   Refer to Section 5.4 for details on operation resources.

5.1.5.  /restconf/streams

   This optional resource is a container that provides access to the
   notification event streams supported by the server.  The server MAY
   omit this resource if no notification event streams are supported.
   The media type for this resource is "application/yang.api".

   The server will populate this container with a stream list entry for
   each stream type it supports.  Each stream contains a leaf called
   "events" which represents an event stream resource.  The media type
   for this resource is "application/yang.stream".  Refer to Section 2.2
   for details on notifications.

5.2.  Datastore Resource

   A datastore resource represents the conceptual root of a tree of data
   resources.  The media type for this resource is "application/
   yang.datastore".  A datastore resource can be retrieved with the GET
   method.

   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 MUST 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 MUST be changed to a new
   previously unused value if changes to any configuration data
   resources within the datastore are made.

   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 3.8.1 for more



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   details.

   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
   retrieved as the target resource with the GET or HEAD methods.  If
   maintained, the resource entity tag MUST 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.  Configuration
   data resources can be accessed via the "/restconf/config" entry
   point.  Operational data resources can be accessed via the
   "/restconf/operational" entry point.

   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 3.8.1 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.



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           +-------+-------------------------------------------+
           | 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
   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.



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   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].

   o  resource URI values returned in Location headers for data
      resources MUST identify the module name, even if there are no
      conflicting local names when the resource is created.  This
      ensures 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 ]

     /restconf/config/example-jukebox:jukebox/library/
        artist/Beatles&select=album

     /restconf/config/example-list:newlist/17&
        select=nextlist%2Ffoo%2Fbar%2Facme-list-ext%3Aext-leaf

     /restconf/config/example-list:somelist/the%20key

     /restconf/config/example-list:somelist/the%20key/address

5.3.1.1.  ABNF For Data Resource Identifiers

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










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       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>

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 "/restconf/config" datastore resource is used to access child
   configuration data resources.  The "/restconf/operational" datastore
   resource is used to access child operational data resources.

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



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   descendant nodes within the target resource.

   The format of the "select" parameter string is defined in
   Section 3.8.5.  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:

      POST /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.




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       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:

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

      {
        "example-ops: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.









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

   The server might respond:

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

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

5.5.  Stream Resource

   A stream resource represents a source for system generated event
   notifications.  Each stream is created and modified by the server
   only.  A client can retrieve a stream resource or initiate a long-
   poll server sent event stream, using the procedure specified in
   Section 2.2.3.

   A notification stream functions according to the NETCONF
   Notifications specification [RFC5277].  The "ietf-restconf" YANG
   module contains the "stream" list (/restconf/streams/stream) which
   specifies the syntax and semantics of a stream resource.








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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               |
   | 412 Precondition Failed   | Conditional method is false           |
   | 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.

   YANG Tree Diagram for <errors> Data:

      +--ro errors
         +--ro error
            +--ro error-type       enumeration
            +--ro error-tag        string
            +--ro error-app-tag?   string
            +--ro error-path?      data-resource-identifier
            +--ro error-message?   string
            +--ro error-info

   Example:

   The following example shows an error returned for an "lock-denied"



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   error on a datastore resource.

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

   The server might respond:

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

      {
        "ietf-restconf:errors": {
          "error": {
            "error-type": "protocol",
            "error-tag": "lock-denied",
            "error-message": "Lock failed, lock 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.

   The YANG Patch operation is selected by the client by invoking a
   PATCH method with the YANG Patch media type.  A message body
   representing the YANG Patch input parameters MUST be provided.

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

   YANG Tree Diagram For "application/yang.patch" Media Type

      +--rw yang-patch
      |  +--rw patch-id?   string
      |  +--rw comment?    string
      |  +--rw edit [edit-id]
      |     +--rw edit-id      string
      |     +--rw operation    enumeration
      |     +--rw target       data-resource-identifier
      |     +--rw point?       data-resource-identifier
      |     +--rw where?       enumeration
      |     +--rw value

   A data element representing the YANG Patch Status is returned to the
   client to report the detailed status of the edit operation.  This
   data is identified by the YANG Patch Status media type.

   YANG Tree Diagram For "application/yang.patch-status" Media Type:
















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      +--rw yang-patch-status
         +--rw patch-id?        string
         +--rw (global-status)?
         |  +--:(global-errors)
         |  |  +--ro errors
         |  |
         |  +--:(ok)
         |     +--rw ok?              empty
         +--rw edit-status
            +--rw edit [edit-id]
               +--rw edit-id     string
               +--rw (edit-status-choice)?
                  +--:(ok)
                  |  +--rw ok?         empty
                  +--:(location)
                  |  +--rw location?   inet:uri
                  +--:(errors)
                     +--ro errors

7.1.  Why not use JSON Patch?

   The HTTP 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 modeling
   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.





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

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

   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:




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   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 an "undo" operation to fail.

   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 defines the
   syntax.

7.6.  YANG Patch Examples

7.6.1.  Add Resources: Error

   The following example shows several songs being added to an existing
   album.  Each edit contains one song.  The first song already exists,
   so an error will be reported for that edit.  The rest of the edits
   were not attempted, since the first edit failed.

    Request from client:

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

      {
        "ietf-restconf:yang-patch" : {
          "patch-id" : "add-songs-patch",
          "edit" : [
            {
              "edit-id" : 1,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Bridge Burning",
                  "location" : "/media/bridge_burning.mp3",
                  "format" : "MP3",
                  "length" : 288



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                }
              }
            },
            {
              "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
                }
              }
            }
          ]
        }
      }

    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/yang.patch-status+json

      {
        "ietf-restconf:yang-patch-status" : {
          "patch-id" : "add-songs-patch",
          "edit-status" : {
            "edit" : [
              {
                "edit-id" : 1,



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                "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"
                    }
                  ]
                }
              }
            ]
          }
        }
      }

7.6.2.  Add Resources: Success

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

   o  Each of 2 edits contains one song.

   o  Both edits succeed and new sub-resources are created


    Request from client:

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

      {
        "ietf-restconf:yang-patch" : {
          "patch-id" : "add-songs-patch-2",
          "edit" : [
            {
              "edit-id" : 1,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {



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                  "name" : "Rope",
                  "location" : "/media/rope.mp3",
                  "format" : "MP3",
                  "length" : 259
                }
              }
            },
            {
              "edit-id" : 2,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Dear Rosemary",
                  "location" : "/media/dear_rosemary.mp3",
                  "format" : "MP3",
                  "length" : 269
                }
              }
            }
          ]
        }
      }

    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/yang.patch-status+json

      {
        "ietf-restconf:yang-patch-status" : {
          "patch-id" : "add-songs-patch-2",
          "ok" : [null],
          "edit-status" : {
            "edit" : [
              {
                "edit-id" : 1,
                "location" : "http://example.com/restconf/
                   config/example-jukebox:jukebox/library/artist/
                   Foo%20Fighters/album/Wasting%20Light/song/Rope"
              },
              {
                "edit-id" : 2,
                "location" : "http://example.com/restconf/
                   config/example-jukebox:jukebox/library/artist/



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                   Foo%20Fighters/album/Wasting%20Light/song/
                   Dear%20Rosemary"
              }
            ]
          }
        }
      }

7.6.3.  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 /restconf/config/example-jukebox:jukebox/
        playlist/Foo-One   HTTP/1.1
      Host: example.com
      Accept: application/yang.patch-status+json
      Content-Type: application/yang.patch+json

      {
        "ietf-restconf:yang-patch" : {
          "patch-id" : "move-song-patch",
          "comment" : "Move song 1 after song 3",
          "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/yang.patch-status+json

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





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8.  RESTCONF module

   The "ietf-restconf" module defines conceptual definitions within
   groupings, which are not meant to be implemented as datastore
   contents by a server.

   The "ietf-yang-types" and "ietf-inet_types" modules from [RFC6991]
   are used by this module for some type definitions.

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

   <CODE BEGINS> file "ietf-restconf@2013-10-19.yang"

   module ietf-restconf {
     namespace "urn:ietf: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 (media type
        application/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.



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        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
        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-02.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2013-10-19 {
       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. The data node that
          uses this data type SHOULD define the document root
          for data resource identifiers.  The default document
          root is the target datastore conceptual root node.
          Data resource identifiers are defined relative to
          this document root.";
       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 {



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           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";
           }
           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.";
     }

     typedef revision-identifier {
       type string {
         pattern '\d{4}-\d{2}-\d{2}';
       }
       description
         "Represents a specific date in YYYY-MM-DD format.
          TBD: make pattern more precise to exclude leading zeros.";
     }

     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. Each edit MUST be applied



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            in ascending order, and all edits MUST be applied.
            If any errors occur, then the target datastore MUST NOT
            be changed by the patch operation.

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

            YANG datastore validation (defined in RFC 6020, section 
            8.3.3) is performed after all edits have 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 MUST
            be reported in the reply message.";

         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 comment {
           type string {
             length "0 .. 1024";
           }
           description
             "An arbitrary string provided by the client to describe
              the entire patch.  This value SHOULD be present in any
              audit logging records generated by the server for the
              patch.";
         }

         list edit {
           key edit-id;
           ordered-by user;

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



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           leaf edit-id {
             type string;
             description
               "Arbitrary string index for the edit.
                Error messages returned by the server pertaining
                to a specific edit will be identified by this
                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
                    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.";
               }



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             }
             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 {
             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 {



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                 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.";
           }
         }
       }

     } // 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



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            request message has been processed.";

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

         choice global-status {
           description
             "Report global errors or complete success.
              If there is no case selected then errors
              are reported in the edit-status container.";

           case global-errors {
             uses errors;
             description
               "This container will be present if global
                errors unrelated to a specific edit occurred.";
           }
           leaf ok {
             type empty;
             description
               "This leaf will be present if the request succeeded
                and there are no errors reported in the edit-status
                container.";
           }
         }

         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.  If an edit entry was
                skipped or not reached by the server,
                then this list will not contain a corresponding
                entry for that edit.";

             leaf edit-id {
               type string;
                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'.";
               }
               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
          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



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            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.";
           }

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



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           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
            application/yang.api resource type.";

         container config {
           description
             "Container representing the application/yang.datastore
              resource type. Represents the conceptual root of the
              unified configuration datastore containing YANG data
              nodes. The child nodes of this container are
              configuration data resources (application/yang.data)
              defined as top-level YANG data nodes from the modules
              advertised by the server in /restconf/modules.";
         }

         container operational {
           description
             "Container representing the application/yang.datastore
              resource type. Represents the conceptual root of the
              operational data supported by the server.  The child
              nodes of this container are operational data resources
              (application/yang.data) defined as top-level
              YANG data nodes from the modules advertised by



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              the server in /restconf/modules.";
         }

         container modules {
           description
             "Contains a list of module description entries.
              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 yang:yang-identifier;
               description "The YANG module name.";
             }
             leaf revision {
               type union {
                 type revision-identifier;
                 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 yang:yang-identifier;
               description
                 "List of YANG feature names from this module that are
                  supported by the server.";
             }
             leaf-list deviation {
               type yang:yang-identifier;
               description
                 "List of YANG deviation module names used by this
                  server to modify the conformance of the module
                  associated with this entry.";
             }
           }



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         }

         container operations {
           description
             "Container for all operation resources
              (application/yang.operation),

              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;
                 }
             ";
         }

         container streams {
           description
             "Container representing the notification event streams
              supported by the server.";
            reference
              "RFC 5277, Section 3.4, <streams> element.";

           list stream {
             key name;
             description
               "Each entry describes an event stream supported by
                the server.";

             leaf name {
               type string;
               description "The stream name";
               reference "RFC 5277, Section 3.4, <name> element.";
             }

             leaf description {
               type string;
               description "Description of stream content";
               reference
                 "RFC 5277, Section 3.4, <description> element.";
             }

             leaf replay-support {
               type boolean;



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               description
                 "Indicates if replay buffer supported for this stream";
               reference
                 "RFC 5277, Section 3.4, <replaySupport> element.";
             }

             leaf replay-log-creation-time {
               type yang:date-and-time;
               description
                 "Indicates the time the replay log for this stream
                  was created.";
               reference
                 "RFC 5277, Section 3.4, <replayLogCreationTime>
                  element.";
             }

             leaf events {
               type empty;
               description
                 "Represents the entry point for establishing
                  notification delivery via server sent events.";
             }
           }
         }

         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


     grouping notification {
       description
         "Contains the notification message wrapper definition.";

       container notification {
         description
           "RESTCONF notification message wrapper.";




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         leaf event-time {
           type yang:date-and-time;
           mandatory true;
           description
             "The time the event was generated by the
              event source.";
           reference
             "RFC 5277, section 4, <eventTime> element.";
         }

         /* The YANG-specific notification container is encoded
          * after the 'event-time' element.  The format
          * corresponds to the notificationContent element
          * in RFC 5277, section 4. For example:
          *
          *  module example-one {
          *     ...
          *     notification event1 { ... }
          *
          *  }
          *
          *  Encoded as element 'event1' in the namespace
          *  for module 'example-one'.
          */
       }
     }  // grouping notification

   }

   <CODE ENDS>





















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9.  IANA Considerations

9.1.  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.

        URI: urn:ietf: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

9.2.  application/yang Media Type

   The MIME media type for RESTCONF resources is application/yang.

      Type name: application

      Subtype name: yang

      Required parameters: TBD

      Optional parameters: TBD

      Encoding considerations: TBD

      Security considerations: TBD

      Interoperability considerations: TBD

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










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10.  Security Considerations

   TBD
















































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11.  References

11.1.  Normative References

   [I-D.lhotka-netmod-json]
              Lhotka, L., "Modeling JSON Text with YANG",
              draft-lhotka-netmod-yang-json-02 (work in progress),
              September 2013.

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

   [RFC2396]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", RFC 2396,
              August 1998.

   [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.

   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event
              Notifications", RFC 5277, July 2008.

   [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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   [wd-eventsource]
              Hickson, I., "Server-Sent Events", December 2012.

11.2.  Informative References

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

   [XPATH]    Clark, J. and S. DeRose, "XML Path Language (XPath)
              Version 1.0", World Wide Web Consortium
              Recommendation REC-xpath-19991116, November 1999,
              <http://www.w3.org/TR/1999/REC-xpath-19991116>.







































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Appendix A.  Change Log

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

A.1.  01 to 02

   o  Added Notification Model (section 2.2)

   o  Remove error-action from YANG Patch

   o  Add "comment" and "ok" leafs to yang-patch-status container

   o  Fixed YANG Patch JSON example syntax

   o  Added stream resource type and streams container to /restconf
      container

   o  Removed "vnd" from media type definitions

   o  Changed yang-patch edit list from ascending uint32 key to an
      arbitrary string key and an ordered-by user list.

   o  Several clarifications and corrections

   o  Add YANG tree diagrams

   o  Add application/yang.patch-status media type

   o  Remove redundant "global-errors" container from
      "yang-patch-status" container

   o  Split the /restconf/datastore entry point into 2 entry points
      (config and operational)

   o  Remove the "config" parameter since it is no longer needed after
      datastore is split

A.2.  00 to 01

   o  Removed incorrect /.well-known URI prefix.

   o  Remove incorrect IANA request for well-known URI.

   o  Clarified that API resource type nodes are defined in the ietf-
      restconf namespace.

   o  Changed CamelCase names in example-jukebox.yang to lowercase, and
      updated examples.



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   o  Updated and corrected YANG types in ietf-restconf module.

A.3.  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 IANA section

   o  added YANG Patch

   o  added YANG definitions to ietf-restconf.yang

   o  added Kent Watsen and Rex Fernando as co-authors





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   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 /restconf"; Server will stop at new resource
      type; e.g. yang.api --> yang.datastore returns the datastore as an
      empty node; yang.api --> yang.operation returns the operation name
      as an empty node;









































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Appendix B.  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 /restconf/
      config 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 "/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?

   A: YANG Patch allows the client to control creation order when



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   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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Appendix C.  Open Issues

C.1.  message-id

   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?

C.2.  select parameter

   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?

C.3.  server support verification

   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?

C.4.  error media type

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

C.5.  additional datastores

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

C.6.  PATCH media type discovery

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

C.7.  RESTCONF version

   o  Is the /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?







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C.8.  YANG to resource mapping

   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.

C.9.  .well-known usage

   o  Does RESTCONF need to Use a .well-known link relation to to re-map
      API entry point?

   The client first discovers the server's root for the RESTCONF API.
   In this example, it is "/api/restconf":

       Request
       -------
       GET /.well-known/host-meta users HTTP/1.1
       Host: example.com
       Accept: application/xrd+xml

       Response
       --------
       HTTP/1.1 200 OK
       Content-Type: application/xrd+xml
       Content-Length: nnn


       <XRD xmlns='http://docs.oasis-open.org/ns/xri/xrd-1.0'>
           <Link rel='restconf' href='/api/restconf'/>
       </XRD>

   Once discovering the RESTCONF API root, the client MUST prepend it to
   any access to a RESTCONF resource:















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

       Response
       --------
       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/yang.api+json

       { "version": "1.0" }

C.10.  _self links for HATEOAS support

   o  Should there be a mode where the client can request that the
      resource identifier is returned in a GET request?

C.11.  netconf-state monitoring support

   o  Should long-term RESTCONF operations (i.e.  SSE long-poll) be
      considered sessions wrt/ NETCONF monitoring "session" list?  If
      so, what text is needed in RESTCONF draft to standardize the
      RESTCONF session entries?

C.12.  secure transport

   o  Details to support secure operation over TLS are needed

   o  Security considerations need to be written
















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Appendix D.  Example YANG Module

   The example YANG module used in this document represents a simple
   media jukebox interface.

   YANG Tree Diagram for "example-jukebox" Module

      +--rw jukebox?
         +--rw library
         |  +--rw artist [name]
         |  |  +--rw name     string
         |  |  +--rw album [name]
         |  |     +--rw name     string
         |  |     +--rw genre?   identityref
         |  |     +--rw year?    uint16
         |  |     +--rw song [name]
         |  |        +--rw name        string
         |  |        +--rw location    string
         |  |        +--rw format?     string
         |  |        +--rw length?     uint32
         |  +--ro artist-count?   uint32
         |  +--ro album-count?    uint32
         |  +--rw song-count?     uint32
         +--rw playlist [name]
         |  +--rw name           string
         |  +--rw description?   string
         |  +--rw song [index]
         |     +--rw index    uint32
         |     +--rw id       instance-identifier
         +--rw player
            +--rw gap?   decimal64


     rpcs:


      +---x play
         +--ro input
            +--ro playlist       string
            +--ro song-number    uint32

D.1.  example-jukebox YANG Module

   module example-jukebox {

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




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      organization "Example, Inc.";
      contact "support at example.com";
      description "Example Jukebox Data Model Module";
      revision "2013-10-19" {
        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
           service is available";

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

        container library {



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

              list song {
                key name;

                description



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



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             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.";
            }
          }
        }

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

          leaf gap {



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            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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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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