Network Working Group                                         A. Bierman
Internet-Draft                                                 YumaWorks
Intended status: Standards Track                            M. Bjorklund
Expires: September 23, 2014 January 4, 2015                                  Tail-f Systems
                                                               K. Watsen
                                                        Juniper Networks
                                                             R. Fernando
                                                                   Cisco
                                                          March 22,
                                                            July 3, 2014

                           RESTCONF Protocol
                     draft-ietf-netconf-restconf-00
                     draft-ietf-netconf-restconf-01

Abstract

   This document describes a REST-like an HTTP-based 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 September 23, 2014. January 4, 2015.

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   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Secure Transport . . . . . . . . . . . . . . . . . . . . .  5
     1.2.  Simple Subset of NETCONF Functionality . . . . . . . . . .  5
     1.2.
     1.3.  Data Model Driven API  . . . . . . . . . . . . . . . . . .  6
     1.3.
     1.4.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  8
       1.3.1.
       1.4.1.  NETCONF  . . . . . . . . . . . . . . . . . . . . . . .  8
       1.3.2.
       1.4.2.  HTTP . . . . . . . . . . . . . . . . . . . . . . . . .  8
       1.3.3.
       1.4.3.  YANG . . . . . . . . . . . . . . . . . . . . . . . . .  9
       1.3.4.
       1.4.4.  Terms  . . . . . . . . . . . . . . . . . . . . . . . .  9
       1.3.5. 10
       1.4.5.  Tree Diagrams  . . . . . . . . . . . . . . . . . . . . 11
   2.  Operations . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     2.1.  OPTIONS  . . . . . . . . . . . . . . . . . . . . . . . . . 12
     2.2.  HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     2.3.  GET  . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     2.4.  POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
       2.4.1.  Create Resource Mode . . . . . . . . . . . . . . . . . 14
       2.4.2.  Invoke Operation Mode  . . . . . . . . . . . . . . . . 15
     2.5.  PUT  . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     2.6.  PATCH  . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     2.7.  DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 19 18
     2.8.  Query Parameters . . . . . . . . . . . . . . . . . . . . . 19
   3.  Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     3.1.  Request URI Structure  . . . . . . . . . . . . . . . . . . 21
     3.2.  Message Headers  . . . .  RESTCONF Path Resolution . . . . . . . . . . . . . . . . . 22
     3.3.  Message Encoding Headers  . . . . . . . . . . . . . . . . . . . . . 23
     3.4.  RESTCONF Meta-Data  Message Encoding . . . . . . . . . . . . . . . . . . . . 23
       3.4.1.  JSON Encoding of . 24
     3.5.  RESTCONF Meta-Data . . . . . . . . . 24
     3.5. . . . . . . . . . . . 25
     3.6.  Return Status  . . . . . . . . . . . . . . . . . . . . . . 26
     3.6. 25
     3.7.  Message Caching  . . . . . . . . . . . . . . . . . . . . . 26 25
   4.  Resources  . . . . . . . . . . . . . . . . . . . . . . . . . . 27 26
     4.1.  RESTCONF Resource Types  . . . . . . . . . . . . . . . . . 27 26
     4.2.  Resource Discovery . . . . . . . . . . . . . . . . . . . . 28 27
     4.3.  API Resource (/restconf) . . . . . . . . . . . . . . . . . 28
       4.3.1.  /restconf/data . . . . . . . . . . . . . . . . . . . . 29
       4.3.2.  /restconf/modules  . . 27
       4.3.1.  {+restconf}/data . . . . . . . . . . . . . . . . 30
       4.3.3.  /restconf/operations . . . 28
       4.3.2.  {+restconf}/modules  . . . . . . . . . . . . . . 31
       4.3.4.  /restconf/streams . . . 29
       4.3.3.  {+restconf}/operations . . . . . . . . . . . . . . . 31
       4.3.5.  /restconf/version . 30
       4.3.4.  {+restconf}/streams  . . . . . . . . . . . . . . . . . 31 30
     4.4.  Datastore Resource . . . . . . . . . . . . . . . . . . . . 31 30
       4.4.1.  Edit Collision Detection . . . . . . . . . . . . . . . 32 31
     4.5.  Data Resource  . . . . . . . . . . . . . . . . . . . . . . 33 31
       4.5.1.  Encoding YANG Instance Identifiers in the Request
               URI  . . . . . . . . . . . . . . . . . . . . . . . . . 33 32
       4.5.2.  Defaults Handling  . . . . . . . . . . . . . . . . . . 36 34
     4.6.  Operation Resource . . . . . . . . . . . . . . . . . . . . 36 35
       4.6.1.  Encoding Operation Input Parameters  . . . . . . . . . 37 35
       4.6.2.  Encoding Operation Output Parameters . . . . . . . . . 38 36
     4.7.  Schema Resource  . . . . . . . . . . . . . . . . . . . . . 39 37
     4.8.  Stream Resource  . . . . . . . . . . . . . . . . . . . . . 39 38
     4.9.  Errors Resource  . . . . . . . . . . . . . . . . . . . . . 38
   5.  Notifications  . . . . . . . . . . . . . . . . . . . . . . . . 41 39
     5.1.  Server Support . . . . . . . . . . . . . . . . . . . . . . 41 39
     5.2.  Event Streams  . . . . . . . . . . . . . . . . . . . . . . 41 39
     5.3.  Subscribing to Receive Notifications . . . . . . . . . . . 42 40
       5.3.1.  NETCONF Event Stream . . . . . . . . . . . . . . . . . 43 41
     5.4.  Receiving Event Notifications  . . . . . . . . . . . . . . 43 41
   6.  Error Reporting  . . . . . . . . . . . . . . . . . . . . . . . 45 43
     6.1.  Error Response Message . . . . . . . . . . . . . . . . . . 46 44
   7.  RESTCONF module  . . . . . . . . . . . . . . . . . . . . . . . 49 47
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 63 61
     8.1.  The "restconf" Relation Type . . . . . . . . . . . . . . . 61
     8.2.  YANG Module Registry . . . . . . . . . . . . . . . . . . . 63
     8.2. 61
     8.3.  application/yang Media Sub Types . . . . . . . . . . . . . 63 61
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 65 63
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 66 64
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 66 64
     10.2. Informative References . . . . . . . . . . . . . . . . . . 67 65
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 68 66
     A.1.  bierman:restconf-04 to ietf:restconf-00  00 - 01  . . . . . . . . . 68
   Appendix B.  Open Issues . . . . . . . . . . . . . . . . 66
     A.2.  bierman:restconf-04 to ietf:restconf-00  . . . . . 69
     B.1.  message-id . . . . 67
   Appendix B.  Open Issues . . . . . . . . . . . . . . . . . . . . 69
     B.2. . 68
     B.1.  select parameter . . . . . . . . . . . . . . . . . . . . . 69
     B.3.  server 68
     B.2.  netconf-state monitoring support verification  . . . . . . . . . . . . . . . 69
     B.4.  error media type 68
     B.3.  secure transport . . . . . . . . . . . . . . . . . . . . . 69
     B.5.  additional datastores  . . . . . . . . . . . . . . . . . . 69
     B.6.  PATCH media type discovery . . . . . . . . . . . . . . . . 70
     B.7.  RESTCONF version . . . . . . . . . . . . . . . . . . . . . 70
     B.8.  YANG to 68
     B.4.  Encoding of key leafs in resource mapping . . . . . . . . . . . . . . . . . 70
     B.9.  .well-known usage  . . . . . . . . . . . . . . . . . . . . 70
     B.10. _self links for HATEOAS support  . URIs . . . . . . . . . . 68
     B.5.  get-bulk query parameters  . . 72
     B.11. netconf-state monitoring support . . . . . . . . . . . . . 72
     B.12. secure transport . 69
     B.6.  defaults handling  . . . . . . . . . . . . . . . . . . . . 72
     B.13. Encoding of key leafs in resource 69
     B.7.  protocol capability URIs . . . . . . . . . . 72
     B.14. get-bulk query parameters  . . . . . . . . . . . . . . . . 73
     B.15. JSON encoding of meta-data . . . . . . . . 69
     B.8.  target resource list keys required for GET . . . . . . . . 73 70
   Appendix C.  Example YANG Module . . . . . . . . . . . . . . . . . 74 71
     C.1.  example-jukebox YANG Module  . . . . . . . . . . . . . . . 74 71
   Appendix D.  RESTCONF Message Examples . . . . . . . . . . . . . . 80 77
     D.1.  Resource Retrieval Examples  . . . . . . . . . . . . . . . 80 77
       D.1.1.  Retrieve the Top-level API Resource  . . . . . . . . . 80 77
       D.1.2.  Retrieve The Server Module Information . . . . . . . . 82 79
     D.2.  Edit Resource Examples . . . . . . . . . . . . . . . . . . 84 81
       D.2.1.  Create New Data Resources  . . . . . . . . . . . . . . 84 81
       D.2.2.  Detect Resource Entity Tag Change  . . . . . . . . . . 85 82
     D.3.  Query String Parameter Examples  . . . . . . . . . . . . . 85 82
       D.3.1.  "content" Parameter  . . . . . . . . . . . . . . . . . 85 82
       D.3.2.  "depth" Parameter  . . . . . . . . . . . . . . . . . . 88 85
       D.3.3.  "filter" Parameter . . . . . . . . . . . . . . . . . . 91 88
       D.3.4.  "insert" Parameter . . . . . . . . . . . . . . . . . . 92 89
       D.3.5.  "point" Parameter  . . . . . . . . . . . . . . . . . . 93 90
       D.3.6.  "select" Parameter . . . . . . . . . . . . . . . . . . 93 90
       D.3.7.  "start-time" Parameter . . . . . . . . . . . . . . . . 94 91
       D.3.8.  "stop-time" Parameter  . . . . . . . . . . . . . . . . 94 91
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 95 92

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 REST-like an HTTP [RFC2616] based 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, protocol
   operations, and notification events.  REST-like  RESTCONF uses HTTP operations are used
   to access the hierarchical data within a datastore.

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

   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 is encoded with either XML [W3C.REC-xml-20081126]
   or JSON [JSON].

   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  Secure Transport

   RESTCONF relies on TLS [RFC2246] to provide privacy and meta-model used data
   integrity for a REST-like its HTTP operations.  More specifically, RESTCONF
   requires HTTP over TLS (HTTPS) [RFC2818].  To ensure security,
   RESTCONF clients MUST verify the RESTCONF server's X.509 certificate
   using the path validation algorithm defined in section 6 of
   [RFC5280].  Devices that do not support TLS will be unable to
   implement RESTCONF.

1.2.  Simple Subset of NETCONF Functionality

   The framework and meta-model used for an HTTP-based 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
   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 REST-like API

   RESTCONF is not intended to replace NETCONF, but rather provide an
   additional simplified interface that follows REST-like REST principles and is
   compatible with a resource-oriented device abstraction.

   The following figure shows the system components:

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

1.2.

1.3.  Data Model Driven API

   RESTCONF combines the simplicity of a REST-like API over the HTTP protocol with the
   predictability and automation potential of a schema-driven API.
   Using YANG, a client can predict all resource endpoints, much like
   using URI Templates [RFC6570], but in a more holistic manner.  This
   strategy obviates the need for responses provided by the server to
   contain HATEOAS links, originally described in Roy Fielding's
   doctoral dissertation [rest-dissertation].

   A REST-like REST 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 with
   regards to 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.

   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.

   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" "{+restconf}/modules" in the top-level API resource
   type, using a structure based on the YANG module capability URI
   format defined in [RFC6020].

   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 ordering behavior is
   derived from the YANG "ordered-by" statement.

   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.

1.3.

1.4.  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.

1.4.1.  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

   o  running configuration datastore

   o  server

   o  startup configuration datastore

   o  state data

   o  user

1.3.2.

1.4.2.  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

   o  request URI

   o  response body

1.3.3.

   o  resource

1.4.3.  YANG

   The following terms are defined in [RFC6020]:

   o  container

   o  data node

   o  key leaf

   o  leaf

   o  leaf-list

   o  list

   o  presence container (or P-container)

   o  RPC operation (now called protocol operation)

   o  non-presence container (or NP-container)

   o  ordered-by system

   o  ordered-by user

1.3.4.

1.4.4.  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.  All YANG data node types
      can be data resources.  YANG terminal nodes cannot contain sub- child
      resources.

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

   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 (Server-Sent Events) event stream.
      The content consists of text using the media type "text/
      event-stream", as defined by the HTML5 specification.  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  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".

   o  patch: a generic PATCH method request on the target datastore or data
      resource.  The media type of the message body content will
      identify the patch type in use.

   o  plain patch: a PATCH method request 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  requested data nodes: the set of data resources identified by the
      target resource, or the "select" query parameter if it is present.

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

   o  retrieval request: a request 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  schema resource: a resource with the media type "application/
      yang".  The YANG representation of the schema can be retrieved by
      the client with the GET method.

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

1.3.5.

1.4.5.  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
      data (read-write) and "ro" state data (read-only).

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

   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.

2.  Operations

   The RESTCONF protocol uses HTTP methods to identify the CRUD
   operation requested for a particular resource.

   The following table shows how the RESTCONF operations relate to
   NETCONF protocol operations:

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

                     Table 1: CRUD Methods in RESTCONF

   The NETCONF "remove" operation attribute is not supported by the HTTP
   DELETE method.  The resource must exist or the DELETE method will
   fail.  The PATCH method is equivalent to a "merge" operation for a
   plain PATCH method. patch.

   Access control mechanims mechanisms may be used to limit what operations can be
   used.  In particular, RESTCONF is compatible with the NETCONF Access
   Control Model (NACM) [RFC6536], as there is a specific mapping
   between RESTCONF and NETCONF operations, defined in Table 1.  The
   resource path 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.

   Implementation of all methods (except PATCH) are defined in
   [RFC2616].  This section defines the RESTCONF protocol usage for each
   HTTP method.

2.1.  OPTIONS

   The OPTIONS method is sent by the client to discover which methods
   are supported by the server for a specific resource.  If supported,
   it SHOULD be implemented for all media types.

   The server SHOULD implement this method, however the same information
   could be extracted from the YANG modules and the RESTCONF protocol
   specification.

   If the PATCH method is supported, then the "Accept-Patch" header MUST
   be supported, as defined in [RFC5789].

2.2.  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.

   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.

2.3.  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 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" or
   "404 Not Found" 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/data/example-jukebox:jukebox/
        library/artist/Foo%20Fighters/album
        library/artist=Foo%20Fighters/album  HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+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

      {
        "album" : [
          {
            "name" : "Wasting Light",
            "genre" : "example-jukebox:alternative",
            "year" : 2011
          }
        ]
      }

   Refer to @ex-create@ for more resource creation examples.

2.4.  POST

   The POST method is sent by the client to create a data resource or
   invoke an operation resource.  The server uses the target resource
   media type to determine how to process the request.

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

                     Resource Types that Support POST

   The request MUST contain a request URI that contains a target
   resource which identifies a datastore, data, or operation resource
   type.

2.4.1.  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. child resource.
   The message body is expected to contain the content of a child
   resource to create within the parent (target resource).

   The "insert" and "point" query parameters are supported by the POST
   method for datastore and data resource types, as specified in the
   YANG definition in Section 7.

   If the POST method succeeds, a "201 Created" Status-Line is returned
   and there is no response message body.  A "Location" header
   identifying the child resource that was created MUST be present in
   the response in this case.

   If the user is not authorized to create the target resource, an error
   response containing a "403 Forbidden" or "404 Not Found" Status-Line
   is returned to the client.  All other error responses are handled
   according to the procedures defined in Section 6.

   Example:

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

      POST /restconf/data 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:

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

   Refer to Appendix D.2.1 for more resource creation examples.

2.4.2.  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 4.6 for details on operation resources.

   If the POST method request 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" or "404 Not Found"
   Status-Line is returned to the client.  All other error responses are
   handled according to the procedures defined in Section 6.

   Example:

   In this example, the client is invoking the "play" operation defined
   in the "example-jukebox" YANG module.

   A client might send a "play" request as follows:

      POST /restconf/operations/example-jukebox:play   HTTP/1.1
      Host: example.com
      Content-Type: application/yang.operation+json

      {
        "example-jukebox:input" : {
          "playlist" : "Foo-One",
          "song-number" : 2
        }
      }

   The server might respond:

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

2.5.  PUT

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

   The request MUST contain a request URI that contains a only target resource media type that identifies supports PUT is the data resource
   resource.  The message body is expected to contain the content used
   to create or replace.

   If the resource instance does not exist, and it represents a valid
   instance the server could create with a POST request, then the server
   SHOULD create it.

   The message body is expected to contain the content used to create or
   replace replace the target resource.

   The "insert" and "point" query parameters are supported by the PUT
   method for data resources, as specified in the YANG definition in
   Section 7.

   Consistent with [RFC2616], if the PUT method request creates a new resource,
   a "201 Created" Status-Line is returned.  If an existing resource is
   modified, either "200 OK" or "204 No Content" are returned.

   If the user is not authorized to create or replace the target
   resource an error response containing a "403 Forbidden" or "404 Not
   Found" Status-Line is returned to the client.  All other error
   responses are handled according to the procedures defined in
   Section 6.

   Example:

   An "album" sub-resource child resource defined in the "example-jukebox" YANG
   module is replaced or created if it does not already exist.

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

      PUT /restconf/data/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light
         library/artist=Foo%20Fighters/album=Wasting%20Light   HTTP/1.1
      Host: example.com
      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

2.6.  PATCH

   The PATCH method

   RESTCONF uses the HTTP PATCH method defined in [RFC5789] to provide
   an extensible framework for resource patching mechanisms.  It is
   optional to implement by the server.  Each patch type needs a unique
   media type.  Zero or more PATCH media types MAY be supported by the
   server.

   The "plain patch" PATCH method

   A plain patch is used to create or update a sub- child resource within the
   target resource.  If the target resource instance does not exist, the
   server MUST NOT create it.

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

   If the user is not authorized to alter the target resource an error
   response containing a "403 Forbidden" or "404 Not Found" Status-Line
   is returned to the client.  All other error responses are handled
   according to the procedures defined in Section 6.

   Example:

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

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

      {
        "example-jukebox:album" : {
          "genre" : "example-jukebox:rock",
          "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:

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

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

2.7.  DELETE

   The DELETE method is used to delete the target resource.  If the
   DELETE method request succeeds, a "204 No Content" 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" or "404 Not Found"
   Status-Line is returned to the client.  All other error responses are
   handled according to the procedures defined in Section 6.

   Example:

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

      DELETE /restconf/data/example-jukebox:jukebox/
         library/artist/Foo%20Fighters/album/Wasting%20Light
         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

2.8.  Query Parameters

   Each RESTCONF operation allows zero or more query parameters to be
   present in the request URI.  The specific parameters that are allowed
   depends on the resource type, and sometimes the specific target
   resource used, in the request.

   +------------+----------+-------------------------------------------+
   | Name       | Methods  | Description                               |
   +------------+----------+-------------------------------------------+
   | content    | GET      | Select config and/or non-config data      |
   |            |          | resources                                 |
   | depth      | GET      | Request limited sub-tree depth in the     |
   |            |          | reply content                             |
   | filter     | GET      | Boolean notification filter for           |
   |            |          | event-stream resources                    |
   | insert     | POST,    | Insertion mode for user-ordered data      |
   |            | PUT      | resources                                 |
   | point      | POST,    | Insertion point for user-ordered data     |
   |            | PUT      | resources                                 |
   | select     | GET      | Request a subset of the target resource   |
   |            |          | contents                                  |
   | start-time | GET      | Replay buffer start time for event-stream |
   |            |          | resources                                 |
   | stop-time  | GET      | Replay buffer stop time for event-stream  |
   |            |          | resources                                 |
   +------------+----------+-------------------------------------------+

                         RESTCONF Query Parameters

   Query parameters can be given in any order.  Each parameter can
   appear at most once in a request URI.  A default value may apply if
   the parameter is missing.

   The semantics and syntax for all query parameters are defined in the
   "query-parameters" YANG grouping in Section 7.  The YANG encoding
   MUST be converted to URL-encoded string for use in the request URI.

   Refer to Appendix D.3 for examples of query parameter usage.

3.  Messages

   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.

3.1.  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> /<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 2.

   o  entry: the well-known root of the RESTCONF API configured on this HTTP
      server, discovered by getting the ".well-known/host-meta"
      resource, as described in Section 3.2.  All of the examples in
      this document assume "/restconf" as the discovered RESTCONF API
      root path.  The URI template [RFC6570] syntax "{+restconf}" is
      used to refer to the entry point ("/restconf"). outside of an example.

   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.

   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.

3.2.  RESTCONF Path Resolution

   In line the best practices defined by [get-off-my-lawn], RESTCONF
   enables deployments to specify where the RESTCONF API is located.
   When first connecting to a RESTCONF server, a RESTCONF client MUST
   determine the root of the RESTCONF API.  The client discovers this by
   getting the "/.well-known/host-meta" resource ([RFC6415]) and using
   the <Link> element containing the "restconf" attribute :

      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='/restconf'/>
      </XRD>

   Once discovering the RESTCONF API root, the client MUST prepend it to
   any subsequent request to a RESTCONF resource.  For instance, using
   the "/restconf" path discovered above, the client can now determine
   the operations supported by the the server:

      Request
      -------
      GET /restconf/operations  HTTP/1.1
      Host: example.com
      Accept: application/yang.api+json,
              application/yang.errors+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

      { "operations" : { "play" : [ null ] } }

3.3.  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 2 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:

   +---------------+---------------------------------------------------+
   | 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

3.3.

3.4.  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].  This
   encoding is valid JSON, but also has special encoding rules to
   identify module namespaces and provide consistent type processing of
   YANG data.

   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 in the request, or if is not 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.

3.4.

3.5.  RESTCONF Meta-Data

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

3.4.1.  JSON Encoding of RESTCONF Meta-Data

   The YANG to XML.  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 YANG leaf or leaf-list
      within a resource is encoded as if it were a container for the
      meta-data values and the resource 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 resource name/value pair is repeated inside this
      container, which contains the actual value of the resource.

   Example:

      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 defined in RESTCONF.

      GET /restconf/data/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
          }
        }
      }

3.5. [I-D.lhotka-netmod-json].

3.6.  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.

3.6.

3.7.  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.

4.  Resources

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

   A resource can be considered a collection of conceptual data and the
   set of allowed methods on that data.  It can contain child nodes that
   are nested child
   resources.  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.

   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.

   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.

4.1.  RESTCONF Resource Types

   The RESTCONF protocol defines some application specific a set of application specific media
   types to identify each of the available resource types.  The
   following resource types are defined in RESTCONF:

                +-----------+----------------------------+
                | Resource  | Media Type                 |
                +-----------+----------------------------+
                | API       | application/yang.api       |
                | Datastore | application/yang.datastore |
                | Data      | application/yang.data      |
                | Errors    | application/yang.errors    |
                | Operation | application/yang.operation |
                | Schema    | application/yang           |
                | Stream    | application/yang.stream    |
                +-----------+----------------------------+
                           RESTCONF Media Types

4.2.  Resource Discovery

   A client SHOULD start by retrieving the top-level API resource, using
   the entry point URI "/restconf". defined in Section 3.2.

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

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

4.3.  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 URI "/restconf".

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

      +--rw restconf
         +--rw data
         +--rw modules
         |  +--rw module module* [name revision]
         |     +--rw name         yang:yang-identifier
         |     +--rw revision     union
         |     +--rw schema?      empty
         |     +--rw namespace    inet:uri
         |     +--rw feature*     yang:yang-identifier
         |     +--rw deviation*   yang:yang-identifier
         |     +--rw submodule submodule* [name revision]
         |        +--rw name        yang:yang-identifier
         |        +--rw revision    union
         |        +--rw schema?     empty
         +--rw operations
         +--rw streams
         |
            +--rw stream 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

   The "restconf" container definition in the "ietf-restconf" module
   defined in Section 7 is used to specify the structure and syntax of
   the conceptual sub-resources child resources within the API resource.

   This resource has the following child resources:

            +----------------+--------------------------------+
            | Child Resource | Description                    |
            +----------------+--------------------------------+
            | data           | Contains all data resources    |
            | modules        | YANG module information        |
            | operations     | Data-model specific operations |
            | streams        | Notification event streams     |
            | version        | RESTCONF API version           |
            +----------------+--------------------------------+

                            RESTCONF Resources

4.3.1.  /restconf/data  {+restconf}/data

   This mandatory resource represents the combined configuration and
   operational data resources that can be accessed by a client.  It
   cannot be created or deleted by the client.  The datastore resource
   type is defined in Section 4.4.

   Example:

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

      GET /restconf/data/example-jukebox:jukebox/library
         ?content=nonconfig  HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+json

   The server might respond:

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

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

4.3.2.  /restconf/modules  {+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.

4.3.2.1.  /restconf/modules/module  {+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 7.

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

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

4.3.3.  /restconf/operations  {+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.

   Operation resources are defined in Section 4.6.

4.3.4.  /restconf/streams  {+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".

   Stream resources are defined in Section 4.8.  Notifications are
   defined in Section 5.

4.3.5.  /restconf/version

   This sub-resource can be used by the client to identify the exact
   version of the RESTCONF protocol implemented by the server.  The same
   server-wide response MUST be returned each time this resource is
   retrieved.

   The value is assigned by the server when the server is started.  The
   server MUST return the value "1.0" for this version of the RESTCONF
   protocol.  This resource is encoded with the rules for an
   "enumeration" data type, using the "version" leaf definition in
   Section 7.

4.4.  Datastore Resource

   The /restconf/data "{+restconf}/data" subtree represents the datastore resource
   type, which is a collection of configuration and operational data
   nodes.

   A "unified datastore" interface is used to simplify resource editing
   for the client.  The RESTCONF unified datastore is a conceptual
   interface to the native configuration datastores that are present on
   the device.

   The underlying NETCONF datastores (i.e., candidate, running, startup)
   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.

   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.

   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.

4.4.1.  Edit Collision Detection

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

4.4.1.1.  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.

   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.

4.4.1.2.  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 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.

4.5.  Data Resource

   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.]
   Each RESTCONF edit of represents 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.

4.5.  Data Resource

   A data resource represents a YANG data node YANG data node that is a descendant node
   of a datastore 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.  If
   maintained, the resource timestamp MUST be set to the current time
   whenever the resource or any configuration resource within the
   resource is altered.

   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 updated whenever the
   resource or any configuration resource within the resource is
   altered.

   A data resource can be retrieved with the GET method.  Data resources
   can be
   are accessed via the "/restconf/data" "{+restconf}/data" entry point.  This sub-tree
   is used to retrieve and edit data resources.

   A configuration data resource can be altered by the client with some
   of
   or all of the edit operations, depending on the target resource and
   the specific operation.  Refer to Section 2 for more details on edit
   operations.

   The resource definition version for a data resource is identified by
   the revision date of the YANG module containing the YANG definition
   for the data resource, specified in the /restconf/modules sub-tree. "{+restconf}/modules" sub-
   tree.

4.5.1.  Encoding YANG Instance Identifiers in the Request URI

   In YANG, data nodes are named with an absolute XPath expression,
   defined in [XPath] , starting from the document root to the target
   resource.  In RESTCONF, URL encoded Location header expressions are
   used instead.

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

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

               RESTCONF instance-identifier Type Conversion

   The "path" component of the request URI contains the absolute path
   expression that identifies the target resource.

   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 4.5.1.1.  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 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 MUST be omitted, encoded according to the operation.  For example,
   the POST method to create a new data resource for a list node does
   not require key values to be present in the request URI.
   following rules.

   o  The key leaf values for a data resource representing a YANG list
      MUST be encoded as follows: using one path segment [RFC3986].

   o  The  If there is only one key leaf value, the path segment is
      constructed by having the list name followed by an "=" followed by
      the single key leaf value.

   o  If there are multiple key leaf values, the value of each leaf
      identified in the "key" statement is encoded in order. the order
      specified in the YANG "key" statement, with a comma separating
      them.

   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  Quoted strings are supported in
      Section 4.5.1.1, according to the encoding rules for the data type
      of the key leaf.

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

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

   o  All whitespace leaf values.  Quoted
      strings 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]. used to express empty strings. (example:
      list=foo,'',baz).

   o  The JSON encoding is "list-instance" ABNF rule defined in [I-D.lhotka-netmod-json].

   o  The entire "key-value" MUST be properly URL-encoded, according to Section 4.5.1.1
      represents the rules defined in [RFC3986]. syntax of a list instance identifier.

   o  resource  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/data/example-jukebox:jukebox/library/
        artist/Beatles/album

     /restconf/data/example-list:newlist/17
        /nextlist%2Ffoo%2Fbar%2Facme-list-ext%3Aext-leaf

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

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

4.5.1.1.  ABNF

      container top {
           list list1 {
           key "key1 key2 key3";
           ...
           list list2 {
               key "key4 key5";
               ...
               leaf X { type string; }
           }
       }

   For the above YANG definition, URI with key leaf values will be
   encoded as follows (line wrapped for display purposes only):

       /restconf/data/top/list1=key1val,key2val,key3val3/
          list2=key4val,key5val/X

4.5.1.1.  ABNF For Data Resource Identifiers

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

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

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

       module-name = identifier

       list-instance = api-identifier "=" key-value ["," key-value]*

       key-value = string

       string = <a quoted or unquoted or empty string>

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

       string = <an unquoted string>

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

4.5.2.  Defaults Handling

   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.  Applications that
   require full control of defaults might consider NETCONF instead of
   RESTCONF.

   If the target of a GET method 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.

   If the target of a GET method is a data node that represents a
   container or list that has any sub-resources child resources with default values,
   for the sub-resources child resources that have not been given value yet, the
   server MAY return the default values that are in use by the server.

4.6.  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.

4.6.1.  Encoding Operation Input Parameters

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

   Example:

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

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

   The client might send the following POST request message:

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

4.6.2.  Encoding Operation Output Parameters

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

   Example:

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

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

   The client might send the following POST request message:

      POST /restconf/operations/example-ops:get-reboot-info HTTP/1.1
      Host: example.com
      Accept: application/yang.operation+json application/yang.operation+json,
              application/yang.errors+json

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 25 Apr 2012 11:10:30 GMT
      Server: example-server
      Content-Type: application/yang.operation+json

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

4.7.  Schema Resource

   If the server supports the "schema" leaf within the API then the
   client can retrieve the YANG schema text for the associated YANG
   module or submodule, using the GET method.

   The client might send the following GET request message:

      GET /restconf/modules/module/example-jukebox/2013-12-21/schema /restconf/modules/module=example-jukebox,2014-07-03/schema
         HTTP/1.1
      Host: example.com
      Accept: application/yang application/yang,
              application/yang.errors+json

   The server might respond:

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

      module example-jukebox {

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

         // rest of YANG module content deleted...
      }

4.8.  Stream Resource

   A stream "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 5.3.

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

4.9.  Errors Resource

   An "errors" resource is a collection of error information that is
   sent as the message body in a server response message, if an error
   occurs while processing a request message.

   The "ietf-restconf" YANG module contains the "errors" grouping which
   specifies the syntax and semantics of an errors resource.  RESTCONF
   error handling behavior is defined in Section 6.

5.  Notifications

   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.

5.1.  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/ "{+restconf}/
   streams" resource described below.  The server does not support
   RESTCONF notifications if an HTTP error code is returned (e.g. (e.g., 404
   Not Found).

5.2.  Event Streams

   A RESTCONF server that supports notifications will populate a stream
   resource for each notification delivery service access point.  A
   RESTCONF client can retrieve the list of supported event streams from
   a RESTCONF server using the GET operation on the "/restconf/streams" "{+restconf}/
   streams" resource.

   The "/restconf/streams" "{+restconf}/streams" container definition in the "ietf-restconf"
   module defined in Section 7 is used to specify the structure and
   syntax of the conceptual sub-resources child resources within the "streams"
   resource.

   For example:

   The client might send the following request:

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

   The server might send the following response:

      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>

5.3.  Subscribing to Receive Notifications

   RESTCONF clients can subscribe to receive notifications by sending an
   HTTP GET request for the "/restconf/streams/stream/<stream-name>" "{+restconf}/streams/stream/<stream-name>"
   resource, with the "Accept" type "text/event-stream".  The server
   will treat the connection as an event stream, using the Server Sent
   Events [wd-eventsource] transport strategy.

   The server MAY support query parameters for a GET method on this
   resource.  These parameters are specific to each notification stream.

   For example:

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

5.3.1.  NETCONF Event Stream

   The server SHOULD support the "NETCONF" notification stream defined
   in [RFC5277].  For this stream, RESTCONF notification subscription
   requests MAY specify parameters indicating the events it wishes to
   receive.

                 +------------+-------------------------+
                 | Name       | Description             |
                 +------------+-------------------------+
                 | start-time | replay event start time |
                 | stop-time  | replay event stop time  |
                 | filter     | boolean content filter  |
                 +------------+-------------------------+

                      NETCONF Stream Query Parameters

   The semantics and syntax for these query parameters are defined in
   the "query-parameters" YANG grouping in Section 7.  The YANG encoding
   MUST be converted to URL-encoded string for use in the request URI.

   Refer to Appendix D.3.3 for filter parameter examples.

5.4.  Receiving Event Notifications

   RESTCONF notifications are encoded according to the definition of the
   event stream.  The NETCONF stream defined in [RFC5277] is encoded in
   XML format.

   The structure of the event data is based on the "notification"
   element definition in section 4 of [RFC5277].  It MUST conform to the
   "notification" YANG container definition in Section 7.

   An example SSE notification encoded using XML:

      data: <notification
      data:    xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
      data:    <event-time>2013-12-21T00:01:00Z</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>

   Since XML is not whitespace sensitive, the above message can be
   encoded onto a single line.

   For example: ('\' line wrapping added for formatting only)

      data: <notification xmlns="urn:ietf:params:xml:ns:yang:ietf-rest\
      conf"><event-time>2013-12-21T00:01:00Z</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>

   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.

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.

                 +-------------------------+-------------+
                 | <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"), "403 Forbidden"), then the server SHOULD send a response
   body containing the information described by the "errors" container
   definition within the YANG module Section 7.  The Content-Type of
   this response message MUST be application/yang.errors.

   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-node)?
            |  +--:(error-path)
            |  |  +--ro error-path?      instance-identifier
            |  +--:(error-urlpath)
            |     +--ro error-urlpath?   data-resource-identifier
            +--ro error-message?   string
            +--ro error-info

   The semantics and syntax for RESTCONF error messages are defined in
   the "errors" YANG grouping in Section 7.

   Examples:

   The following example shows an error returned for an "lock-denied"
   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 application/yang.errors+json

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

   The following example shows an error returned for a "data-exists"
   error on a data resource.  The "jukebox" resource already exists so
   it cannot be created.

   The client might send:

      POST /restconf/data/example-jukebox:jukebox 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 application/yang.errors+json

      {
        "ietf-restconf:errors": {
          "error": {
            "error-type": "protocol",
            "error-tag": "data-exists",
            "error-urlpath": "http://example.com/restconf/data/
                 example-jukebox:jukebox",
            "error-message":
              "Data already exists, cannot create new resource"
          }
        }
      }

7.  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" "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@2014-03-22.yang" "ietf-restconf@2014-07-03.yang"

   module ietf-restconf {
     namespace "urn:ietf:params:xml:ns:yang:ietf-restconf";
     prefix "rc";

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

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

     contact
       "WG Web:   <http://tools.ietf.org/wg/netconf/>
        WG List:  <mailto:netconf@ietf.org>

        WG Chair: Bert Wijnen
                  <mailto:bertietf@bwijnen.net>

        WG Chair: Mehmet Ersue
                  <mailto:mehmet.ersue@nsn.com>

        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 message and error content that is used in
        RESTCONF protocol messages. A conceptual container
        representing the RESTCONF API nodes is also defined
        for the 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.

        Copyright (c) 2014 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-ietf-netconf-restconf-00.txt draft-ietf-netconf-restconf-01.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2014-03-22 2014-07-03 {
       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 resource instance.
          The document root for all data resources is a
          datastore resource container. Each top-level YANG
          data nodes supported by the server will be represented
          as a child node of the document root.

          The canonical representation of a data resource identifier
          includes the full server specification that is returned
          in the Location header when a new data resource is created
          with the POST method.

          The abbreviated representation does not contain any server
          location identification. Instead the identifier will start
          with the '/' character to represent the datastore document
          root for the data resource instance.

          The server MUST accept either representation and SHOULD
          return the canonical representation in any response message.";
       reference
         "RFC XXXX: [sec. 5.3.1.1 ABNF For Data Resource Identifiers]";
     }

     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 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
            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.";
           }

           choice error-node {
             description
               "The server will return the location of the error node
                in a format that is appropriate for the protocol.
                If no specific node within the request message body
                caused the error then this choice will not be present.";

             leaf error-path {
               type instance-identifier;
               description
                 "The YANG instance identifier associated
                  with the error node. This leaf will only be
                  present if the error node is not a data resource,
                  e.g., the error node is an input parameter
                  for an operation resource.";
             }
             leaf error-urlpath {
               type data-resource-identifier;
               description
                 "The target data resource identifier associated
                  with the error node.  This leaf will only be
                  present if the error node is associated with
                  a data resource (either within the server or
                  in the request message).";
             }
           }

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

           anyxml error-info {
              description
                "Arbitrary XML that represents a container
                 of additional information for the error report.";
           }
         }
       }
     } // 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 data {
           description
             "Container representing the application/yang.datastore
              resource type. Represents the conceptual root of all
              operational data and configuration data supported by
              the server.  The child nodes of this container can be
              any data resource (application/yang.data), which are
              defined as top-level data nodes from the YANG modules
              advertised by the server in /restconf/modules.";
         }
         container modules {
           description
             "Contains a list of module description entries.
              These modules are currently loaded into the server.";

           grouping common-leafs {
             description
               "Common parameters for YANG modules and submodules.";

             leaf name {
               type yang:yang-identifier;
               description "The YANG module or submodule name.";
             }
             leaf revision {
               type union {
                 type revision-identifier;
                 type string { length 0; }
               }
               description
                 "The YANG module or submodule revision date.
                  An empty string is used if no revision statement
                  is present in the YANG module or submodule.";
             }

             leaf schema {
               type empty;
               description
                 "Represents the YANG schema resource for this module
                  or submodule if it is available on the server.
                  This leaf will only be present if the server has
                  the schema available for retrieval.  A GET
                  request with a target resource URI that identifies
                  this leaf will cause the server to return the YANG
                  schema text for the associated module or submodule.";
             }
           }

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

             uses common-leafs;

             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.";
             }

             list submodule {
               key "name revision";
               description
                 "Each entry represents one submodule within the
                  parent module.";

               uses common-leafs;
             }
           }
         }

         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;
               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 query-parameters {
       description
          "Contains conceptual definitions for the query string
           parameters used in the RESTCONF protocol.";

       leaf content {
         type enumeration {
           enum config {
             description
               "Return only configuration descendant data nodes";
           }
           enum nonconfig {
             description
               "Return only non-configuration descendant data nodes";
           }
           enum all {
             description
               "Return all descendant data nodes";
           }
         }
         description
            "The content parameter controls how descendant nodes of
             the requested data nodes will be processed in the reply.

             This parameter is only allowed for GET methods on
             datastore and data resources.  A 400 Bad Request error
             is returned if used for other methods or resource types.

             The default value is determined by the config-stmt
             value of the requested data nodes. If 'false', then
             the default is 'nonconfig'.  If 'true' then the
             default is 'config'.";
       }

       leaf depth {
         type union {
           type enumeration {
             enum unbounded {
               description "All sub-resources will be returned.";
             }

           }
           type uint32 {
             range "1..max";
           }
         }
         default unbounded;
         description
           "The 'depth' parameter is used to specify the number
            of nest levels returned in a response for a GET method.
            The first nest-level consists of the requested data node
            itself. Any child nodes which are contained within
            a parent node have a depth value that is 1 greater than
            its parent.

            This parameter is only allowed for GET methods on api,
            datastore, and data resources.  A 400 Bad Request error
            is returned if used for other methods or resource types.

            By default, the server will include all sub-resources
            within a retrieved resource, which have the same resource
            type as the requested resource. Only one level of
            sub-resources with a different media type than the target
            resource will be returned.";
       }

       leaf filter {
         type yang:xpath1.0;
         description
           "The '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.

            This parameter is only allowed for GET methods on a
            text/event-stream data resource.  A 400 Bad Request error
            is returned if used for other methods or resource types.

            The format of this parameter is an XPath expression, and
            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.";
       }

       leaf insert {
         type enumeration {
           enum first {
             description "Insert the new data as the new first entry.";
           }
           enum last {
             description "Insert the new data as the new last entry.";
           }
           enum before {
             description
               "Insert the new data before the insertion point,
                specified by the value of the 'point' parameter.";
           }
           enum after {
             description
               "Insert the new data after the insertion point,
                specified by the value of the 'point' parameter.";
           }
         }
         default last;
         description
           "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 and PUT
            methods. It is also only supported if the target
            resource is a data resource, and that data represents
            a YANG list or leaf-list that is ordered by the user.

            If the values 'before' or 'after' are used,
            then a 'point' query parameter for the insertion
            parameter MUST also be present, or a 400 Bad Request
            error is returned.";
       }

       leaf point {
         type data-resource-identifier;
         description
           "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 or leaf-list.

            This parameter is only supported for the POST and PUT
            methods. It is also only supported if the target
            resource is a data resource, and that data represents
            a YANG list or leaf-list that is ordered by the user.

            If the 'insert' query parameter is not present, or has
            a value other than 'before' or 'after', then a 400
            Bad Request error is returned.

            This parameter contains the instance identifier of the
            resource to be used as the insertion point for a
            POST or PUT method.";
       }

       leaf select {
         type string {
           length "1 .. max";
         }
         description
           "The 'select' query parameter is used to specify an
            expression which can represent a subset of all optionally identify
            data nodes within the target resource. It contains an expression
            string, using the target resource as the context node. to be retrieved in a
            GET method.  The encoding for client can use this parameter to retrieve
            a subset of all nodes in a resource.

            A value of the select 'select' query parameter matches the
            following rule:

              select-expr = path '(' select-expr / '*' ')' /
                            path ';' select-expr /
                            path
              path = api-identifier [ '/' path ]

            'api-identifier' is still TBD. defined in section 5.3.1.1.

            ';' is used to select multiple nodes.  For example, to
            retreive only the 'genre' and 'year' of an album, use:
            'select=genre;year'.

            Parentheses are used to specify sub-selectors of a node.
            For example, to retreive only the 'label' and
            'catalogue-number' of an album, use:
            'select=admin(label;catalogue-number)'.

            '/' is used in a path to retreive a child node of a node.
            For example, to retreive only the 'label' of an album, use:
            'select=admin/label'.

            This parameter is only allowed for GET methods on api,
            datastore, and data resources.  A 400 Bad Request error
            is returned if used for other methods or resource types.

            If XPath:
            The string is an XPath expression that will be evaluated
            using the target resource instance as the context node
            and the document root. It is expected to return a node-set
            result representing the descendants within the context
            node that should be returned in a GET response."; types.";
       reference
         "RFC XXXX: [sec. 5.3.1.1 ABNF For Data Resource Identifiers]";
       }

       leaf start-time {
         type yang:date-and-time;
         description
           "The 'start-time' parameter is used to trigger
            the notification 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.

            This parameter is only allowed for GET methods on a
            text/event-stream data resource.  A 400 Bad Request error
            is returned if used for other methods or resource types.

            If this parameter is not present, then a replay subscription
            is not begin requested.  It is not valid to specify start
            times that are later than the current time.  If the value
            specified is earlier than the log can support, the replay
            will begin with the earliest available notification";
       }

       leaf stop-time {
         type yang:date-and-time;
         description
           "The 'stop-time' parameter is used with the
            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.

            This parameter is only allowed for GET methods on a
            text/event-stream data resource.  A 400 Bad Request error
            is returned if used for other methods or resource types.

            If this parameter is not present, the notifications will
            continue until the subscription is terminated.
            Values in the future are valid.";
       }

     }  // grouping query-parameters
     grouping notification {
       description
         "Contains the notification message wrapper definition.";

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

         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>

8.  IANA Considerations

8.1.  The "restconf" Relation Type

   This specification registers the "restconf" relation type in the Link
   Relation Type Registry defined by [RFC5988]:

      Relation Name:  restconf

      Description:  Identifies the root of RESTCONF API as configured
                    on this HTTP server.  The "restconf" relation
                    defines the root of the API defined in RFCXXXX.
                    Subsequent revisions of RESTCONF will use alternate
                    relation values to support protocol versioning.

      Reference:  RFC XXXX

   `

8.2.  YANG Module Registry

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

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

8.2.

8.3.  application/yang Media Sub Types

   The parent MIME media type for RESTCONF resources is application/
   yang, which is defined in [RFC6020].  This document defines the
   following sub-types for this media type.

      - api
      - data
      - datastore
      - errors
      - operation
      - stream

      Type name: application

      Subtype name: yang.xxx

      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

9.  Security Considerations

   TBD

10.  References

10.1.  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.

   [JSON]     Bray, T., Ed., "The JSON Data Interchange Format",
              draft-ietf-json-rfc4627bis-10 (work

   This section provides security considerations for the resources
   defined by the RESTCONF protocol.  Security considerations for HTTPS
   are defined in progress),
              December 2013.

   [RFC2119]  Bradner, S., "Key words [RFC2818].  Security considerations for use the content
   manipulated by RESTCONF can be found 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 the documents defining data
   models.

   This document does not specify an authentication scheme, but it does
   require that an authenticated NETCONF username be associated with
   each HTTP request.  The authentication scheme MAY be implemented in
   the underlying transport layer (e.g., client certificates) or within
   the HTTP layer (e.g., Basic Auth, OAuth, etc.).  RESTCONF does not
   itself define an authentication mechanism, authentication MUST occur
   in a lower layer.  Implementors SHOULD provide a comprehensive
   authorization scheme with RESTCONF and ensure that the resulting
   NETCONF username is made available to the RESTCONF server.

   Authorization of individual user access to operations and data MAY be
   configured via NETCONF Access Control Model (NACM) [RFC6536], as
   specified in Section 2.  Other authorization models MAY be used, but
   are outside of the scope of this document.

   Configuration information is by its very nature sensitive.  Its
   transmission in the clear and without integrity checking leaves
   devices open to classic eavesdropping and false data injection
   attacks.  Configuration information often contains passwords, user
   names, service descriptions, and topological information, all of
   which are sensitive.  Because of this, this protocol SHOULD be
   implemented carefully with adequate attention to all manner of attack
   one might expect to experience with other management interfaces.

   Different environments may well allow different rights prior to and
   then after authentication.  When an operation is not properly
   authorized, the RESTCONF server MUST return HTTP error status code
   401 Unauthorized.  Note that authorization information can be
   exchanged in the form of configuration information, which is all the
   more reason to ensure the security of the connection.

10.  References

10.1.  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.

   [JSON]     Bray, T., Ed., "The JSON Data Interchange Format",
              draft-ietf-json-rfc4627bis-10 (work in progress),
              December 2013.

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

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol, Version 1.0",
              RFC 2246, January 1999.

   [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.

   [RFC2818]  Rescorla, E., "The IETF XML Registry", RFC 2818, May 2000.

   [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.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and T. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

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

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988, October 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.

   [RFC6415]  Hammer-Lahav, E. and B. Cook, "Web Host Metadata",
              RFC 6415, October 2011.

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

   [RFC6570]  Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
              and D. Orchard, "URI Template", RFC 6570, March 2012.

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

   [W3C.REC-xml-20081126]
              Yergeau, F., Maler, E., Paoli, J., Sperberg-McQueen, C.,
              and T. Bray, "Extensible Markup Language (XML) 1.0 (Fifth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20081126, November 2008,
              <http://www.w3.org/TR/2008/REC-xml-20081126>.

   [get-off-my-lawn]
              Nottingham, M., "URI Design and Ownership", Best Current
              Practice draft-ietf-appsawg-uri-get-off-my-lawn-05,
              May 2014.

   [rest-dissertation]
              Fielding, R., "Architectural Styles and the Design of
              Network-based Software Architectures", 2000.

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

10.2.  Informative References

   [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>.

Appendix A.  Change Log

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

A.1.  bierman:restconf-04 to ietf:restconf-00  00 - 01

   o  updated open issues section

Appendix B.  Open Issues

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

B.1.  message-id  fixed content=nonconfig example (non-config was incorrect)

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

   Status: open

B.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?

   Status: solution proposal pending from Martin

B.3.  server support verification does not apply.

   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?

   Status:  closed

   Resolution: no concern the methods or open issue 'server support verification'.  The headers used
      by RESTCONF are
   not widely supported.

B.4.  error media type

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

   Status: closed-update-needed; Consensus is that a new media type for
   <errors>  removed encoding rules from section on RESTCONF Meta-Data.  This
      is needed.

B.5.  additional datastores now defined in [I-D.lhotka-netmod-json].

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

   Status: closed
   Resolution: Exposing the candidate and startup datastores is not
   needed.  A single unified datastore can probably be used for future
   extensions, depending on how the future extension is designed.

B.6.  PATCH media type discovery

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

   Status: closed-update-pending

   Resolution: the Accept-Patch header defined in RFC 5789 needs map to be
   implemented by the server errors YANG
      grouping.  Updated error examples to advertise the use new media types supported for
   PATCH.

B.7.  RESTCONF version type.

   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  closed open issue 'additional datastores'.  Support may be added
      in the ietf-restconf
      YANG module revision date, instead of future to identify new datastores.

   o  closed open issue 'PATCH media type discovery'.  The section on
      PATCH has an added sentence on the string 1.0?

   Status: Accept-Patch header.

   o  closed open

B.8.  YANG issue 'YANG to resource mapping'.  Current mapping

   o  Since of
      all data nodes to resources can only be YANG containers or lists, what
      should will be done about top-level used in order to allow
      mandatory DELETE support.  The PATCH operation is optional, as
      well as the YANG data nodes Patch media type.

   o  closed open issue '_self links for HATEOAS support'.  It was
      decided that they are not
      containers or lists?  Are redundant because they allowed in RESTCONF?

   Status: closed

   Resolution: top-level terminal nodes can be resources.  Current
   definition of all levels are new sub-resources for server
   implementation purposes

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

   Status: closed

   Resolution: choices are not resources

B.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 module for the server's root specific data.

   o  added explanatory text for the 'select' parameter.

   o  added 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 Path Resolution section for discovering the RESTCONF API root, the client MUST prepend it to
   any access to a RESTCONF resource:

       Request
       -------
       GET /api/restconf/version  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" }

   Status: closed

   Resolution: this is not needed in the root of
      the RESTCONF

B.10.  _self links API using the /.well-known/host-meta.

   o  added an "error" media type to for HATEOAS support structured error messages

   o  Should there  added Secure Transport section requiring TLS

   o  added Security Considerations section

   o  removed all references to "REST-like"

A.2.  bierman:restconf-04 to ietf:restconf-00

   o  updated open issues section

Appendix B.  Open Issues

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

B.1.  select parameter

   o  What syntax should be a mode where used for the client can request that "select" query parameter?  The
      current choices are "XPath" and "path-expr".  Perhaps an
      additional parameter to identify the
      resource identifier select string format is returned in a GET request?
      needed to allow extensibility?

   Status: closed

   Resultion: these links are not needed.  RESTCONF is REST-like, not
   REST-ful.

B.11. solution proposal added by Martin.

B.2.  netconf-state monitoring support

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

   Status: closed-update-pending

   Resolution:

   A new data structure to monitor streams can be added to the netconf-
   state sub-tree.  The session-id in this new data structure is not
   restricted to the NETCONF-only rules for the sessions sub-tree.

B.12.

B.3.  secure transport

   o  Details to support secure operation over TLS are needed

   Status: open closed

   o  Security considerations need to be written

   Status: open closed

   o  Can call-home for RESTCONF be supported

   Status: open

B.13.

B.4.  Encoding of key leafs in resource URIs

   o  The use of a forward slash '/' as the delimiter between key values delimiter between key values
      in a target resource URI is not not desirable.  Only 1 segment per
      YANG data node layer should be used.

   Status: open

   Proposals:

   Example: list foo, int8 keys X and Y

   Old:

     /restconf/data/foo/19/22/foo-leaf

   New:

     /restconf/data/foo=19,22/foo-leaf

   Or:

     /restconf/data/foo/19,22/foo-leaf

B.5.  get-bulk query parameters

   o  New query parameters (e.g., offset, limit) are needed to retrieve
      a limited number of list instances.

   Status: solution proposal pending

   Resolution: This bulk retrieval mechanism will be added.

B.6.  defaults handling

   o  The client does not really know what sort of defaults the server
      will return in GET replies.  Should the with-defaults query
      parameter be added to RESTCONF?  If so, should it be mandatory-to-
      implement?

   Status: open

B.7.  protocol capability URIs

   o  The client does not know what vendor extensions (if any) are
      implemented by the server.  Should the server provide a read-only
      container of capability URIs to identify protocol extensions?  The
      NETMOD WG may also want to extend the protocol in a the future
      without updating the core RESTCONF RFC.

   Status: open

B.8.  target resource URI is not not desirable.  Only 1 segment per
      YANG data node layer should be used.

   Status: closed-update-pending

   Resolution:

   Example: list foo, int8 keys X and Y

   Old:

     /restconf/datastore/foo/19/22/foo-leaf

   New:

     /restconf/datastore/foo=19,22/foo-leaf

B.14.  get-bulk query parameters required for GET

   o  New query parameters (e.g., offset, limit) are needed  Should the client be able to retrieve GET all or a limited number subset of all list instances.

   Status: solution proposal pending

   Resolution: This bulk retrieval mechanism will be added.

B.15.  JSON encoding of meta-data
      instances by issuing a GET without any list keys for the target
      resource list?

     GET /restconf/data/interfaces/interface

   o  Should the encoding rules for protocol meta-data a "collection" resource be moved required in order for such a
      request to be considered valid by the
      YANG to JSON draft? server.

   Status: open

Appendix C.  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 admin
         |  |     |  +--rw label?              string
         |  |     |  +--rw catalogue-number?   string
         |  |     +--rw song [name]
         |  |        +--rw name        string
         |  |        +--rw location    string
         |  |        +--rw format?     string
         |  |        +--rw length?     uint32
         |  +--ro artist-count?   uint32
         |  +--ro album-count?    uint32
         |  +--ro 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

C.1.  example-jukebox YANG Module

   module example-jukebox {
      namespace "http://example.com/ns/example-jukebox";
      prefix "jbox";
      import ietf-restconf { prefix rc; }

      organization "Example, Inc.";
      contact "support at example.com";
      description "Example Jukebox Data Model Module";
      revision "2013-12-21" "2014-07-03" {
        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 {

          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";
              }
              container admin {
                description
                  "Administrative information for the album.";

                leaf label {
                  type string;
                  description "The label that released the album.";
                }
                leaf catalogue-number {
                  type string;
                  description "The album's catalogue number.";
                }
              }

              list song {
                key name;

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

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

            }   // end list 'album'
          }  // end list 'artist'

          leaf artist-count {
             type uint32;
             units "songs";
             config false;
             description "Number of artists in the library";
          }
          leaf album-count {
             type uint32;
             units "albums";
             config false;
             description "Number of albums in the library";
          }
          leaf song-count {
             type uint32;
             units "songs";
             config false;
             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 rc:data-resource-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 {
            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";
          }
        }
      }
   }

Appendix D.  RESTCONF Message Examples

   The examples within this document use the normative YANG module
   defined in Section 7 and the non-normative example YANG module
   defined in Appendix C.1.

   This section shows some typical RESTCONF message exchanges.

D.1.  Resource Retrieval Examples

D.1.1.  Retrieve the Top-level API Resource

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

      GET /restconf   HTTP/1.1
      Host: example.com
      Accept: application/yang.api+json application/yang.api+json,
              application/yang.errors+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.api+json

      {
        "ietf-restconf:restconf": {
          "data" : [ null ],
          "modules": {
            "module": [
              {
                "name" : "example-jukebox",
                "revision" : "2013-12-21", "2014-07-03",
                "namespace" : "http://example.com/ns/example-jukebox",
                "schema" : [ null ]
              }
            ]
          },
          "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 application/yang.api+xml,
              application/yang.errors+xml

   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">
        <data/>
        <modules>
          <module>
            <name>example-jukebox</name>
            <revision>2013-12-21</revision>
            <revision>2014-07-03</revision>
            <namespace>
              http://example.com/ns/example-jukebox
            </namespace>
            <schema />
          </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>

D.1.2.  Retrieve The Server Module Information

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

      GET /restconf/modules  HTTP/1.1
      Host: example.com
      Accept: application/yang.api+json application/yang.api+json,
              application/yang.errors+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",
              "schema" : [null],
              "namespace" : "http://example.com/ns/foo",
              "feature" : [ "feature1", "feature2" ]
            },
            {
              "name" : "foo-types",
              "revision" : "2012-01-05",
              "schema" : [null],
              "namespace" : "http://example.com/ns/foo-types"
            },
            {
              "name" : "bar",
              "revision" : "2012-11-05",
              "schema" : [null],
              "namespace" : "http://example.com/ns/bar",
              "feature" : [ "bar-ext" ],
              "submodule" : [
                {
                  "name" : "bar-submod1",
                  "revision" : "2012-11-05",
                  "schema" : [null]
                },
                {
                  "name" : "bar-submod2",
                  "revision" : "2012-11-05",
                  "schema" : [null]
                }
              ]
            }
          ]
        }
      }

D.2.  Edit Resource Examples

D.2.1.  Create New Data Resources

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

      POST /restconf/data/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/data/
           example-jukebox:jukebox/library/artist/Foo%20Fighters
           example-jukebox:jukebox/library/artist=Foo%20Fighters
      Last-Modified: Mon, 23 Apr 2012 17:02:00 GMT
      ETag: b3830f23a4c

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

      POST /restconf/data/example-jukebox:jukebox/
         library/artist/Foo%20Fighters
         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/data/
        example-jukebox:jukebox/library/artist/Foo%20Fighters/
        album/Wasting%20Light
        example-jukebox:jukebox/library/artist=Foo%20Fighters/
        album=Wasting%20Light
      Last-Modified: Mon, 23 Apr 2012 17:03:00 GMT
      ETag: b8389233a4c

D.2.2.  Detect Resource Entity Tag Change

   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 patch an "album" list entry with key value
   "Wasting Light".  Only the "year" field is being updated.

      PATCH /restconf/data/example-jukebox:jukebox/
        library/artist/Foo%20Fighters/album/Wasting%20Light/year
        library/artist=Foo%20Fighters/album=Wasting%20Light/year
        HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+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

D.3.  Query String Parameter Examples

D.3.1.  "content" Parameter

   The "content" parameter is used to select the type of data sub- child
   resources (configuration and/or not configuration) that are returned
   by the server for a GET method request.

   In this example, a simple YANG list that has configuration and non-
   configuration sub-resources. child resources.

     container events
       list event {
         key name;
         leaf name { type string; }
         leaf description { type string; }
         leaf event-count {
           type uint32;
           config false;
         }
       }
     }

   Example 1: content=all

   To retrieve all the sub-resources, child resources, the "content" parameter is set
   to "all".  The client might send:

      GET /restconf/data/example-events:events?content=all
          HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+json

   The server might respond:

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

      {
        "example-events:events" : {
          "event" : [
            {
              "name" : "interface-up",
              "description" : "Interface up notification count",
              "event-count" : 42
            },
            {
              "name" : "interface-down",
              "description" : "Interface down notification count",
              "event-count" : 4
            }
          ]
        }
      }

   Example 2: content=config

   To retrieve only the configuration sub-resources, child resources, the "content"
   parameter is set to "config" or omitted since this is the default
   value.  Note that the "ETag" and "Last-Modified" headers are only
   returned if the content parameter value is "config".

      GET /restconf/data/example-events:events?content=config
         HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+json

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:11:30 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
      ETag: eeeada438af
      Cache-Control: no-cache
      Pragma: no-cache
      Content-Type: application/yang.data+json

      {
        "example-events:events" : {
          "event" : [
            {
              "name" : "interface-up",
              "description" : "Interface up notification count"
            },
            {
              "name" : "interface-down",
              "description" : "Interface down notification count"
            }
          ]
        }
      }

   Example 3: content=non-config content=nonconfig

   To retrieve only the non-configuration sub-resources, child resources, the "content"
   parameter is set to "non-config". "nonconfig".  Note that configuration ancestors
   (if any) and list key leafs (if any) are also returned.  The client
   might send:

      GET /restconf/data/example-events:events?content=non-config /restconf/data/example-events:events?content=nonconfig
         HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+json

   The server might respond:

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

      {
        "example-events:events" : {
          "event" : [
            {
              "name" : "interface-up",
              "event-count" : 42
            },
            {
              "name" : "interface-down",
              "event-count" : 4
            }
          ]
        }
      }

D.3.2.  "depth" Parameter

   The "depth" parameter is used to limit the number of levels of sub- child
   resources that are returned by the server for a GET method request.

   This example shows how different values of the "depth" parameter
   would affect the reply content for retrieval of the top-level
   "jukebox" data resource.

   Example 1: depth=unbounded

   To retrieve all the sub-resources, child resources, the "depth" parameter is not
   present or set to the default value "unbounded".  Note that some
   strings are wrapped for display purposes only.

      GET /restconf/data/example-jukebox:jukebox?depth=unbounded
         HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+json

   The server might respond:

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

      {
        "example-jukebox:jukebox" : {
          "library" : {
            "artist" : [
              {
                "name" : "Foo Fighters",
                "album" : [
                  {
                    "name" : "Wasting Light",
                    "genre" : "example-jukebox:alternative",
                    "year" : 2011,
                    "song" : [
                      {
                        "name" : "Wasting Light",
                        "location" :
                          "/media/foo/a7/wasting-light.mp3",
                        "format" : "MP3",
                        "length" " 286
                      },
                      {
                        "name" : "Rope",
                        "location" : "/media/foo/a7/rope.mp3",
                        "format" : "MP3",
                        "length" " 259
                      }
                    ]
                  }
                ]
              }
            ]
          },
          "playlist" : [
            {
              "name" : "Foo-One",
              "description" : "example playlist 1",
              "song" : [
                {
                  "index" : 1,
                  "id" : "http://example.com/restconf/data/
                        example-jukebox:jukebox/library/artist/
                        Foo%20Fighters/album/Wasting%20Light/
                        song/Rope"
                },
                {
                  "index" : 2,
                  "id" : "http://example.com/restconf/data/
                        example-jukebox:jukebox/library/artist/
                        Foo%20Fighters/album/Wasting%20Light/song/
                        Bridge%20Burning"
                }
              ]
            }
          ],
          "player" : {
            "gap" : 0.5
          }
        }
      }

   Example 2: depth=1

   To determine if 1 or more resource instances exist for a given target
   resource, the value "1" is used.

      GET /restconf/data/example-jukebox:jukebox?depth=1 HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+json

   The server might respond:

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

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

   Example 3: depth=3

   To limit the depth level to the target resource plus 2 sub-resource child resource
   layers the value "3" is used.

      GET /restconf/data/example-jukebox:jukebox?depth=3 HTTP/1.1
      Host: example.com
      Accept: application/yang.data+json application/yang.data+json,
              application/yang.errors+json

   The server might respond:

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

      {
        "example-jukebox:jukebox" : {
          "library" : {
            "artist" : [ null ]
          },
          "playlist" : [
            {
              "name" : "Foo-One",
              "description" : "example playlist 1",
              "song" : [ null ]
            }
          ],
          "player" : {
            "gap" : 0.5
          }
        }
      }

D.3.3.  "filter" Parameter

   The following URIs show some examples of notification filter
   specifications (lines wrapped for display purposes only):

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

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

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

      // filter = /*/reportingEntity/card!='Ethernet0'
      GET /restconf/streams/stream/NETCONF/events? /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? /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? /restconf/streams/stream=NETCONF/events?
        filter=(%2Fexample-mod%3Aevent1%2Fname%3D'joe'%20and
                %20%2Fexample-mod%3Aevent1%2Fstatus%3D'online')

D.3.4.  "insert" Parameter

   In this example, a new first entry in the "Foo-One" playlist is being
   created.

   Request from client:

      POST /restconf/data/example-jukebox:jukebox/
        playlist/Foo-One?insert=first
        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/data/
         example-jukebox:jukebox/playlist/Foo-One/song/1
         example-jukebox:jukebox/playlist=Foo-One/song=1
      ETag: eeeada438af

D.3.5.  "point" Parameter

   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.

   Request from client:

      POST /restconf/data/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/foo/a7/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

D.3.6.  "select" Parameter

   TBD

   In this example the client is retrieving the API resource, but
   selecting only the "name" and "revision" nodes from each module, in
   JSON format:

      GET /restconf?select=modules/module(name;revision) HTTP/1.1
      Host: example.com
      Accept: application/yang.api+json,
              application/yang.errors+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.api+json

      {
        "ietf-restconf:restconf": {
          "modules": {
            "module": [
              {
                "name" : "example-jukebox",
                "revision" : "2014-07-03"
              }
            ]
          }
        }
      }

D.3.7.  "start-time" Parameter

   TBD

D.3.8.  "stop-time" Parameter

   TBD

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