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Versions: (draft-bierman-netconf-restconf) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 RFC 8040

Network Working Group                                         A. Bierman
Internet-Draft                                                 YumaWorks
Intended status: Standards Track                            M. Bjorklund
Expires: January 8, 2017                                  Tail-f Systems
                                                               K. Watsen
                                                        Juniper Networks
                                                            July 7, 2016


                           RESTCONF Protocol
                     draft-ietf-netconf-restconf-15

Abstract

   This document describes an HTTP-based protocol that provides a
   programmatic interface for accessing data defined in YANG, using the
   datastore concepts 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 January 8, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.












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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   6
       1.1.1.  NETCONF . . . . . . . . . . . . . . . . . . . . . . .   6
       1.1.2.  HTTP  . . . . . . . . . . . . . . . . . . . . . . . .   6
       1.1.3.  YANG  . . . . . . . . . . . . . . . . . . . . . . . .   7
       1.1.4.  NETCONF Notifications . . . . . . . . . . . . . . . .   7
       1.1.5.  Terms . . . . . . . . . . . . . . . . . . . . . . . .   7
       1.1.6.  URI Template and Examples . . . . . . . . . . . . . .  10
       1.1.7.  Tree Diagrams . . . . . . . . . . . . . . . . . . . .  10
     1.2.  Subset of NETCONF Functionality . . . . . . . . . . . . .  10
     1.3.  Data Model Driven API . . . . . . . . . . . . . . . . . .  11
     1.4.  Coexistence with NETCONF  . . . . . . . . . . . . . . . .  12
     1.5.  RESTCONF Extensibility  . . . . . . . . . . . . . . . . .  13
   2.  Transport Protocol Requirements . . . . . . . . . . . . . . .  14
     2.1.  Integrity and Confidentiality . . . . . . . . . . . . . .  14
     2.2.  HTTPS with X.509v3 Certificates . . . . . . . . . . . . .  14
     2.3.  Certificate Validation  . . . . . . . . . . . . . . . . .  14
     2.4.  Authenticated Server Identity . . . . . . . . . . . . . .  15
     2.5.  Authenticated Client Identity . . . . . . . . . . . . . .  15
   3.  Resources . . . . . . . . . . . . . . . . . . . . . . . . . .  15
     3.1.  Root Resource Discovery . . . . . . . . . . . . . . . . .  16
     3.2.  RESTCONF Media Types  . . . . . . . . . . . . . . . . . .  17
     3.3.  API Resource  . . . . . . . . . . . . . . . . . . . . . .  18
       3.3.1.  {+restconf}/data  . . . . . . . . . . . . . . . . . .  19
       3.3.2.  {+restconf}/operations  . . . . . . . . . . . . . . .  19
       3.3.3.  {+restconf}/yang-library-version  . . . . . . . . . .  20
     3.4.  Datastore Resource  . . . . . . . . . . . . . . . . . . .  20
       3.4.1.  Edit Collision Detection  . . . . . . . . . . . . . .  21
     3.5.  Data Resource . . . . . . . . . . . . . . . . . . . . . .  22
       3.5.1.  Timestamp . . . . . . . . . . . . . . . . . . . . . .  22
       3.5.2.  Entity tag  . . . . . . . . . . . . . . . . . . . . .  23
       3.5.3.  Encoding Data Resource Identifiers in the Request URI  23
       3.5.4.  Defaults Handling . . . . . . . . . . . . . . . . . .  26
     3.6.  Operation Resource  . . . . . . . . . . . . . . . . . . .  27
       3.6.1.  Encoding Operation Resource Input Parameters  . . . .  29
       3.6.2.  Encoding Operation Resource Output Parameters . . . .  32



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       3.6.3.  Encoding Operation Resource Errors  . . . . . . . . .  34
     3.7.  Schema Resource . . . . . . . . . . . . . . . . . . . . .  35
     3.8.  Event Stream Resource . . . . . . . . . . . . . . . . . .  36
     3.9.  Errors YANG Data Template . . . . . . . . . . . . . . . .  37
   4.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .  37
     4.1.  OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . .  38
     4.2.  HEAD  . . . . . . . . . . . . . . . . . . . . . . . . . .  38
     4.3.  GET . . . . . . . . . . . . . . . . . . . . . . . . . . .  38
     4.4.  POST  . . . . . . . . . . . . . . . . . . . . . . . . . .  40
       4.4.1.  Create Resource Mode  . . . . . . . . . . . . . . . .  40
       4.4.2.  Invoke Operation Mode . . . . . . . . . . . . . . . .  41
     4.5.  PUT . . . . . . . . . . . . . . . . . . . . . . . . . . .  42
     4.6.  PATCH . . . . . . . . . . . . . . . . . . . . . . . . . .  44
       4.6.1.  Plain Patch . . . . . . . . . . . . . . . . . . . . .  44
     4.7.  DELETE  . . . . . . . . . . . . . . . . . . . . . . . . .  45
     4.8.  Query Parameters  . . . . . . . . . . . . . . . . . . . .  46
       4.8.1.  The "content" Query Parameter . . . . . . . . . . . .  47
       4.8.2.  The "depth" Query Parameter . . . . . . . . . . . . .  47
       4.8.3.  The "fields" Query Parameter  . . . . . . . . . . . .  48
       4.8.4.  The "filter" Query Parameter  . . . . . . . . . . . .  49
       4.8.5.  The "insert" Query Parameter  . . . . . . . . . . . .  50
       4.8.6.  The "point" Query Parameter . . . . . . . . . . . . .  50
       4.8.7.  The "start-time" Query Parameter  . . . . . . . . . .  51
       4.8.8.  The "stop-time" Query Parameter . . . . . . . . . . .  52
       4.8.9.  The "with-defaults" Query Parameter . . . . . . . . .  52
   5.  Messages  . . . . . . . . . . . . . . . . . . . . . . . . . .  53
     5.1.  Request URI Structure . . . . . . . . . . . . . . . . . .  53
     5.2.  Message Encoding  . . . . . . . . . . . . . . . . . . . .  55
     5.3.  RESTCONF Metadata . . . . . . . . . . . . . . . . . . . .  55
       5.3.1.  XML MetaData Encoding Example . . . . . . . . . . . .  56
       5.3.2.  JSON MetaData Encoding Example  . . . . . . . . . . .  56
     5.4.  Return Status . . . . . . . . . . . . . . . . . . . . . .  57
     5.5.  Message Caching . . . . . . . . . . . . . . . . . . . . .  57
   6.  Notifications . . . . . . . . . . . . . . . . . . . . . . . .  57
     6.1.  Server Support  . . . . . . . . . . . . . . . . . . . . .  58
     6.2.  Event Streams . . . . . . . . . . . . . . . . . . . . . .  58
     6.3.  Subscribing to Receive Notifications  . . . . . . . . . .  59
       6.3.1.  NETCONF Event Stream  . . . . . . . . . . . . . . . .  60
     6.4.  Receiving Event Notifications . . . . . . . . . . . . . .  61
   7.  Error Reporting . . . . . . . . . . . . . . . . . . . . . . .  63
     7.1.  Error Response Message  . . . . . . . . . . . . . . . . .  64
   8.  RESTCONF module . . . . . . . . . . . . . . . . . . . . . . .  66
   9.  RESTCONF Monitoring . . . . . . . . . . . . . . . . . . . . .  72
     9.1.  restconf-state/capabilities . . . . . . . . . . . . . . .  73
       9.1.1.  Query Parameter URIs  . . . . . . . . . . . . . . . .  73
       9.1.2.  The "defaults" Protocol Capability URI  . . . . . . .  74
     9.2.  restconf-state/streams  . . . . . . . . . . . . . . . . .  75
     9.3.  RESTCONF Monitoring Module  . . . . . . . . . . . . . . .  75



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   10. YANG Module Library . . . . . . . . . . . . . . . . . . . . .  79
     10.1.  modules-state  . . . . . . . . . . . . . . . . . . . . .  79
       10.1.1.  modules-state/module . . . . . . . . . . . . . . . .  79
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  79
     11.1.  The "restconf" Relation Type . . . . . . . . . . . . . .  79
     11.2.  YANG Module Registry . . . . . . . . . . . . . . . . . .  80
     11.3.  Media Types  . . . . . . . . . . . . . . . . . . . . . .  80
       11.3.1.  Media Type application/yang-data . . . . . . . . . .  80
       11.3.2.  Media Type application/yang-data+json  . . . . . . .  82
     11.4.  RESTCONF Capability URNs . . . . . . . . . . . . . . . .  84
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  84
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  85
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  86
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  86
     14.2.  Informative References . . . . . . . . . . . . . . . . .  89
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  89
     A.1.  v14 to v15  . . . . . . . . . . . . . . . . . . . . . . .  89
     A.2.  v13 - v14 . . . . . . . . . . . . . . . . . . . . . . . .  89
     A.3.  v12 - v13 . . . . . . . . . . . . . . . . . . . . . . . .  91
     A.4.  v11 - v12 . . . . . . . . . . . . . . . . . . . . . . . .  91
     A.5.  v10 - v11 . . . . . . . . . . . . . . . . . . . . . . . .  92
     A.6.  v09 - v10 . . . . . . . . . . . . . . . . . . . . . . . .  93
     A.7.  v08 - v09 . . . . . . . . . . . . . . . . . . . . . . . .  95
     A.8.  v07 - v08 . . . . . . . . . . . . . . . . . . . . . . . .  95
     A.9.  v06 - v07 . . . . . . . . . . . . . . . . . . . . . . . .  95
     A.10. v05 - v06 . . . . . . . . . . . . . . . . . . . . . . . .  96
     A.11. v04 - v05 . . . . . . . . . . . . . . . . . . . . . . . .  96
     A.12. v03 - v04 . . . . . . . . . . . . . . . . . . . . . . . .  97
     A.13. v02 - v03 . . . . . . . . . . . . . . . . . . . . . . . .  97
     A.14. v01 - v02 . . . . . . . . . . . . . . . . . . . . . . . .  98
     A.15. v00 - v01 . . . . . . . . . . . . . . . . . . . . . . . .  99
     A.16. bierman:restconf-04 to ietf:restconf-00 . . . . . . . . .  99
   Appendix B.  Open Issues  . . . . . . . . . . . . . . . . . . . . 100
   Appendix C.  Example YANG Module  . . . . . . . . . . . . . . . . 100
     C.1.  example-jukebox YANG Module . . . . . . . . . . . . . . . 101
   Appendix D.  RESTCONF Message Examples  . . . . . . . . . . . . . 106
     D.1.  Resource Retrieval Examples . . . . . . . . . . . . . . . 106
       D.1.1.  Retrieve the Top-level API Resource . . . . . . . . . 106
       D.1.2.  Retrieve The Server Module Information  . . . . . . . 108
       D.1.3.  Retrieve The Server Capability Information  . . . . . 109
     D.2.  Edit Resource Examples  . . . . . . . . . . . . . . . . . 110
       D.2.1.  Create New Data Resources . . . . . . . . . . . . . . 110
       D.2.2.  Detect Resource Entity Tag Change . . . . . . . . . . 112
       D.2.3.  Edit a Datastore Resource . . . . . . . . . . . . . . 112
       D.2.4.  Edit a Data Resource  . . . . . . . . . . . . . . . . 113
     D.3.  Query Parameter Examples  . . . . . . . . . . . . . . . . 113
       D.3.1.  "content" Parameter . . . . . . . . . . . . . . . . . 113
       D.3.2.  "depth" Parameter . . . . . . . . . . . . . . . . . . 116



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       D.3.3.  "fields" Parameter  . . . . . . . . . . . . . . . . . 119
       D.3.4.  "insert" Parameter  . . . . . . . . . . . . . . . . . 120
       D.3.5.  "point" Parameter . . . . . . . . . . . . . . . . . . 121
       D.3.6.  "filter" Parameter  . . . . . . . . . . . . . . . . . 122
       D.3.7.  "start-time" Parameter  . . . . . . . . . . . . . . . 122
       D.3.8.  "stop-time" Parameter . . . . . . . . . . . . . . . . 122
       D.3.9.  "with-defaults" Parameter . . . . . . . . . . . . . . 123
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 124

1.  Introduction

   There is a need for standard mechanisms to allow Web applications to
   access the configuration data, state data, data-model specific RPC
   operations, and event notifications within a networking device, in a
   modular and extensible manner.

   This document defines an HTTP [RFC7230] based protocol called
   RESTCONF, for configuring data defined in YANG version 1 [RFC6020] or
   YANG version 1.1 [I-D.ietf-netmod-rfc6020bis], using the datastore
   concepts defined in NETCONF [RFC6241].

   NETCONF 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, configuration, state data, RPC operations, and
   event notifications.

   RESTCONF uses HTTP methods to provide CRUD operations on a conceptual
   datastore containing YANG-defined data, which is compatible with a
   server which implements NETCONF datastores.

   If a RESTCONF server is co-located with a NETCONF server, then there
   are protocol interactions to be considered, as described in
   Section 1.4.  The RESTCONF server MAY provide access to specific
   datastores using operation resources, as described in Section 3.6.

   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 [RFC7159].

   Data-model specific RPC operations defined with the YANG "rpc" or
   "action" statements can be invoked with the POST method.  Data-model
   specific event notifications defined with the YANG "notification"
   statement can be accessed.





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1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.1.1.  NETCONF

   The following terms are defined in [RFC6241]:

   o  candidate configuration datastore

   o  configuration data

   o  datastore

   o  configuration datastore

   o  running configuration datastore

   o  startup configuration datastore

   o  state data

   o  user

1.1.2.  HTTP

   The following terms are defined in [RFC3986]:

   o  fragment

   o  path

   o  query

   The following terms are defined in [RFC7230]:

   o  header

   o  message-body

   o  request-line

   o  request URI

   o  status-line




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   The following terms are defined in [RFC7231]:

   o  method

   o  request

   o  resource

   The following terms are defined in [RFC7232]:

   o  entity tag

1.1.3.  YANG

   The following terms are defined in [I-D.ietf-netmod-rfc6020bis]:

   o  action

   o  container

   o  data node

   o  key leaf

   o  leaf

   o  leaf-list

   o  list

   o  mandatory node

   o  ordered-by user

   o  presence container

   o  RPC operation

   o  top-level data node

1.1.4.  NETCONF Notifications

   The following terms are defined in [RFC5277]:

   o  notification replay

1.1.5.  Terms




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   The following terms are used within this document:

   o  API resource: a resource that models the RESTCONF entry point and
      the sub-resources to access YANG-defined content.  It is defined
      with the YANG data template named "yang-api" in the
      "ietf-restconf" module.

   o  data resource: a resource that models a YANG data node.  It is
      defined with YANG data definition statements, and YANG containers,
      leafs, leaf-list entries, list entries, anydata and anyxml nodes
      can be data resources.

   o  datastore resource: a resource that models a programmatic
      interface to NETCONF datastores.  By default, RESTCONF methods
      access a unified view of the underlying datastore implementation
      on the server.  It is defined as a sub-resource within the API
      resource.

   o  edit operation: a RESTCONF operation on a data resource using
      either a POST, PUT, PATCH, or DELETE method.  This is not the same
      as the NETCONF edit operation (i.e., one of the values for the
      "nc:operation" attribute: "create", "replace", "merge", "delete",
      or "remove").

   o  event stream resource: 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 SSE
      [W3C.REC-eventsource-20150203] 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 an event notification stream.  Also called a
      "stream resource".

   o  media-type: HTTP uses Internet media types [RFC2046] in the
      Content-Type and Accept header fields in order to provide open and
      extensible data typing and type negotiation.

   o  NETCONF client: a client which implements the NETCONF protocol.
      Called "client" in [RFC6241].

   o  NETCONF server: a server which implements the NETCONF protocol.
      Called "server" in [RFC6241].

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





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   o  operation resource: a resource that models a data-model specific
      operation, that is defined with a YANG "rpc" or "action"
      statement.  It is invoked with the POST method.

   o  patch: a generic PATCH 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 specific PATCH request type, defined in
      Section 4.6.1, that can be used for simple merge operations.  It
      has a representation with the media-type "application/yang-data"
      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  RESTCONF capability: An optional RESTCONF protocol feature
      supported by the server, which is identified by an IANA registered
      NETCONF Capability URI, and advertised with an entry in the
      "capability" leaf-list in Section 9.3.

   o  RESTCONF client: a client which implements the RESTCONF protocol.
      Also called "client".

   o  RESTCONF server: a server which implements the RESTCONF protocol.
      Also called "server".

   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  schema resource: a resource that has a representation with the
      media type "application/yang".  The schema resource is used by the
      client to retrieve the YANG schema with the GET method.

   o  stream list: the set of data resource instances that describe the
      event stream resources available from the server.  This
      information is defined in the "ietf-restconf-monitoring" module as
      the "stream" list.  It can be retrieved using the target resource
      "{+restconf}/data/ietf-restconf-monitoring:restconf-state/streams/
      stream".  The stream list contains information about each stream,
      such as the URL to retrieve the event stream data.








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   o  YANG data template: a schema for modeling a conceptual data
      structure in an encoding-independent manner.  It is defined with
      the "yang-data" extension, found in Section 8.  It has a
      representation with the media-type "application/yang-data" or
      "application/yang-data+json".

1.1.6.  URI Template and Examples

   Throughout this document, the URI template [RFC6570] syntax
   "{+restconf}" is used to refer to the RESTCONF API entry point
   outside of an example.  See Section 3.1 for details.

   For simplicity, all of the examples in this document assume "/
   restconf" as the discovered RESTCONF API root path.

   Many of the examples throughout the document are based on the
   "example-jukebox" YANG module, defined in Appendix C.1.

1.1.7.  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, "!"
      means a presence container, and "*" denotes a list and 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.

1.2.  Subset of NETCONF Functionality

   RESTCONF does not need to mirror the full functionality of the
   NETCONF protocol, but it does need to be compatible with NETCONF.
   RESTCONF achieves this by implementing a subset of the interaction
   capabilities provided by the NETCONF protocol, for instance, by
   eliminating datastores and explicit locking.






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   RESTCONF uses HTTP methods to implement the equivalent of NETCONF
   operations, enabling basic CRUD operations on a hierarchy of
   conceptual resources.

   The HTTP POST, PUT, PATCH, and DELETE methods are used to edit data
   resources represented by YANG data models.  These basic edit
   operations allow the running configuration to be altered in an all-
   or-none fashion.

   RESTCONF is not intended to replace NETCONF, but rather provide an
   additional interface that follows Representational State Transfer
   (REST) principles [rest-dissertation], and is compatible with a
   resource-oriented device abstraction.

   The following figure shows the system components if a RESTCONF server
   is co-located with a NETCONF server:

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

   The following figure shows the system components if a RESTCONF server
   is implemented in a device that does not have a NETCONF server:

      +-----------+           +-----------------+
      |  Web app  | <-------> |                 |
      +-----------+   HTTP    | network device  |
                              |                 |
                              +-----------------+

1.3.  Data Model Driven API

   RESTCONF combines the simplicity of the HTTP protocol with the
   predictability and automation potential of a schema-driven API.
   Using YANG, a client can predict all management resources, 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 Hypermedia as the Engine of Application State (HATEOAS)
   links, originally described in Roy Fielding's doctoral dissertation
   [rest-dissertation], because the client can determine the links it
   needs from the YANG modules.





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   RESTCONF provides the YANG module capability information supported by
   the server, in case the client wants to use it.  The URIs for data-
   model specific RPC operations and datastore content are predictable,
   based on the YANG module definitions.

   The RESTCONF protocol operates on a conceptual datastore defined with
   the YANG data modeling language.  The server lists each YANG module
   it supports using the "ietf-yang-library" YANG module, defined in
   [I-D.ietf-netconf-yang-library].  The server MUST implement the
   "ietf-yang-library" module, which MUST identify all the YANG modules
   used by the server.

   The conceptual datastore contents, data-model-specific operations and
   event notifications are identified by this set of YANG modules.

   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.

1.4.  Coexistence with NETCONF

   RESTCONF can be implemented on a device that supports NETCONF.

   If the device supports :writable-running, all edits to configuration
   nodes in {+restconf}/data are performed in the running configuration
   datastore.  The URI template "{+restconf}" is defined in
   Section 1.1.6.

   Otherwise, if the device supports :candidate, all edits to
   configuration nodes in {+restconf}/data are performed in the
   candidate configuration datastore.  The candidate MUST be
   automatically committed to running immediately after each successful
   edit.  Any edits from other sources that are in the candidate
   datastore will also be committed.  If a confirmed-commit procedure is
   in progress, then this commit will act as the confirming commit.  If
   the server is expecting a "persist-id" parameter to complete the
   confirmed commit procedure then the RESTCONF edit operation MUST fail
   with a "409 Conflict" status-line.

   If the device supports :startup, the device MUST automatically update
   the non-volatile "startup datastore", after the running datastore has
   been updated as a consequence of a RESTCONF edit operation.




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   If a datastore that would be modified by a RESTCONF operation has an
   active lock from a NETCONF client, the RESTCONF edit operation MUST
   fail with a "409 Conflict" status-line.

1.5.  RESTCONF Extensibility

   There are two extensibility mechanisms built into RESTCONF:

   o  protocol version

   o  optional capabilities

   This document defines version 1 of the RESTCONF protocol.  If a
   future version of this protocol is defined, then that document will
   specify how the new version of RESTCONF is identified.  It is
   expected that a different entry point {+restconf2} would be defined.
   The server will advertise all protocol versions that it supports in
   its host-meta data.

   In this example, the server supports both RESTCONF version 1 and a
   fictitious version 2.

      Request
      -------
      GET /.well-known/host-meta 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'/>
       <Link rel='restconf2' href='/restconf2'/>
   </XRD>

   RESTCONF also supports a server-defined list of optional
   capabilities, which are listed by a server using the
   "ietf-restconf-monitoring" module defined in Section 9.3.  This
   document defines several query parameters in Section 4.8.  Each
   optional parameter has a corresponding capability URI defined in
   Section 9.1.1 that is advertised by the server if supported.

   The "capabilities" list can identify any sort of server extension.
   Typically this extension mechanism is used to identify optional query



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   parameters but it is not limited to that purpose.  For example, the
   "defaults" URI defined in Section 9.1.2 specifies a mandatory URI
   identifying server defaults handling behavior.

   A new sub-resource type could be identified with a capability if it
   is optional to implement.  Mandatory protocol features and new
   resource types require a new revision of the RESTCONF protocol.

2.  Transport Protocol Requirements

2.1.  Integrity and Confidentiality

   HTTP [RFC7230] is an application layer protocol that may be layered
   on any reliable transport-layer protocol.  RESTCONF is defined on top
   of HTTP, but due to the sensitive nature of the information conveyed,
   RESTCONF requires that the transport-layer protocol provides both
   data integrity and confidentiality.  A RESTCONF server MUST support
   the TLS protocol [RFC5246].  The RESTCONF protocol MUST NOT be used
   over HTTP without using the TLS protocol.

   HTTP/2 [RFC7540] MAY be used for RESTCONF.  The server MUST respond
   using a single HTTP/2 stream for all client requests from a stream.
   The server MAY respond using same HTTP/2 stream that was used for the
   corresponding request.

2.2.  HTTPS with X.509v3 Certificates

   Given the nearly ubiquitous support for HTTP over TLS [RFC7230],
   RESTCONF implementations MUST support the "https" URI scheme, which
   has the IANA assigned default port 443.

   RESTCONF servers MUST present an X.509v3 based certificate when
   establishing a TLS connection with a RESTCONF client.  The use the
   X.509v3 based certificates is consistent with NETCONF over TLS
   [RFC7589].

2.3.  Certificate Validation

   The RESTCONF client MUST either use X.509 certificate path validation
   [RFC5280] to verify the integrity of the RESTCONF server's TLS
   certificate, or match the presented X.509 certificate with locally
   configured certificate fingerprints.

   The presented X.509 certificate MUST also be considered valid if it
   matches a locally configured certificate fingerprint.  If X.509
   certificate path validation fails and the presented X.509 certificate
   does not match a locally configured certificate fingerprint, the
   connection MUST be terminated as defined in [RFC5246].



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2.4.  Authenticated Server Identity

   The RESTCONF client MUST check the identity of the server according
   to Section 6 of [RFC6125], including processing the outcome as
   described in Section 6.6 of [RFC6125].

2.5.  Authenticated Client Identity

   The RESTCONF server MUST authenticate client access to any protected
   resource.  If the RESTCONF client is not authenticated, the server
   SHOULD send an HTTP response with "401 Unauthorized" status-line, as
   defined in Section 3.1 of [RFC7235].

   To authenticate a client, a RESTCONF server MUST use TLS based client
   certificates (Section 7.4.6 of [RFC5246]), or MUST use any HTTP
   authentication scheme defined in the HTTP Authentication Scheme
   Registry (Section 5.1 in [RFC7235]).  A server MAY also support the
   combination of both client certificates and an HTTP client
   authentication scheme, with the determination of how to process this
   combination left as an implementation decision.

   The RESTCONF client identity derived from the authentication
   mechanism used is hereafter known as the "RESTCONF username" and
   subject to the NETCONF Access Control Module (NACM) [RFC6536].  When
   a client certificate is presented, the RESTCONF username MUST be
   derived using the algorithm defined in Section 7 of [RFC7589].  For
   all other cases, when HTTP authentication is used, the RESTCONF
   username MUST be provided by the HTTP authentication scheme used.

3.  Resources

   The RESTCONF protocol operates on a hierarchy of resources, starting
   with the top-level API resource itself (Section 3.1).  Each resource
   represents a manageable component within the device.

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

   A resource has a representation associated with a media type
   identifier, as 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 resource types are defined in this document except
   specific datastore contents, RPC operations, and event notifications.



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   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 data model specific RPC operations, top-level data
   nodes, and event notification messages supported by the server.

   The RESTCONF protocol does not include a data 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.

3.1.  Root Resource Discovery

   In line with the best practices defined by [RFC7320], 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.  There MUST be exactly one
   "restconf" link relation returned by the device.

   The client discovers this by getting the "/.well-known/host-meta"
   resource ([RFC6415]) and using the <Link> element containing the
   "restconf" attribute :

   Example returning /restconf:

      Request
      -------
      GET /.well-known/host-meta 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>

   After discovering the RESTCONF API root, the client MUST prepend it
   to any subsequent request to a RESTCONF resource.  In this example,
   the client would use the path "/restconf" as the RESTCONF entry
   point.




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   Example returning /top/restconf:

      Request
      -------
      GET /.well-known/host-meta 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='/top/restconf'/>
   </XRD>

   In this example, the client would use the path "/top/restconf" as the
   RESTCONF entry point.

   The client can now determine the operation resources supported by the
   the server.  In this example a custom "play" operation is supported:

      Request
      -------
      GET /top/restconf/operations  HTTP/1.1
      Host: example.com
      Accept: application/yang-data+json

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

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

   If the XRD contains more than one link relation, then only the
   relation named "restconf" is relevant to this specification.

3.2.  RESTCONF Media Types






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   The RESTCONF protocol defines two application specific media types to
   identify representations of data which conforms to the schema for a
   particular YANG construct.

   This document defines media types for XML and JSON serialization of
   YANG data.  Other documents MAY define other media types for
   different serializations of YANG data.  The "application/yang-data"
   media-type is defined in Section 11.3.1.  The "application/
   yang-data+json" media-type is defined in Section 11.3.2.

3.3.  API Resource

   The API resource contains the entry points for the RESTCONF datastore
   and operation resources.  It is the top-level resource located at
   {+restconf} and has the media type "application/yang-data" or
   "application/yang-data+json".

   YANG Tree Diagram for an API Resource:

   +--rw restconf
      +--rw data
      +--rw operations
      +--ro yang-library-version

   The "yang-api" YANG data template is defined with the "yang-data"
   extension in the "ietf-restconf" module, found in Section 8.  It is
   used to specify the structure and syntax of the conceptual child
   resources within the API resource.

   The API resource can be retrieved with the GET method.

   The {+restconf} entry point resource name used in responses MUST
   identify the "ietf-restconf" YANG module.  For example, a request to
   GET the entry point "/restconf" in JSON format will return a
   representation of the API resource named "ietf-restconf:restconf".

   This resource has the following child resources:

         +----------------------+--------------------------------+
         | Child Resource       | Description                    |
         +----------------------+--------------------------------+
         | data                 | Contains all data resources    |
         | operations           | Data-model specific operations |
         | yang-library-version | ietf-yang-library module date  |
         +----------------------+--------------------------------+

                           RESTCONF API Resource




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3.3.1.  {+restconf}/data

   This mandatory resource represents the combined configuration and
   state 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 3.4.

   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 (see Section 4.8.1).

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

   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
   Content-Type: application/yang-data

   <library xmlns="https://example.com/ns/example-jukebox">
     <artist-count>42</artist-count>
     <album-count>59</album-count>
     <song-count>374</song-count>
   </library>

3.3.2.  {+restconf}/operations

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

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

   The entry point for each RPC operation is represented as an empty
   leaf.  If an operation resource is retrieved, the empty leaf
   representation is returned by the server.

   Operation resources are defined in Section 3.6.



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3.3.3.  {+restconf}/yang-library-version

   This mandatory leaf identifies the revision date of the
   "ietf-yang-library" YANG module that is implemented by this server.

   [RFC Editor Note: Adjust the date for ietf-yang-library below to the
   date in the published ietf-yang-library YANG module, and remove this
   note.]

   Example:

   GET /restconf/yang-library-version  HTTP/1.1
   Host: example.com
   Accept: application/yang-data

   The server might respond (response wrapped for display purposes):

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

   <yang-library-version
     xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library">
     2016-04-09
   </yang-library-version>

3.4.  Datastore Resource

   The "{+restconf}/data" subtree represents the datastore resource
   type, which is a collection of configuration data and state data
   nodes.  The fragment field in the request URI has no defined purpose
   if the target resource is a datastore resource.

   This resource type is an abstraction of the system's underlying
   datastore implementation.  It is used to simplify resource editing
   for the client.  The RESTCONF datastore resource is a conceptual
   collection of all configuration and state data that is present on the
   device.

   Configuration edit transaction management and configuration
   persistence are handled by the server and not controlled by the
   client.  A datastore resource can be written directly with the POST
   and PATCH methods.  Each RESTCONF edit of a datastore resource is
   saved to non-volatile storage by the server, if the server supports
   non-volatile storage of configuration data.




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   If the datastore resource represented by the "{+restconf}/data"
   subtree is retrieved, then the datastore and its contents are
   returned by the server.  The datastore is represented by a node named
   "data" in the "ietf-restconf" module namespace.

3.4.1.  Edit Collision Detection

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

3.4.1.1.  Timestamp

   The last change time is maintained and the "Last-Modified"
   ([RFC7232], Section 2.2) header is 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 SHOULD maintain a last-modified timestamp for the
   datastore resource, defined in Section 3.4.  This timestamp is only
   affected by configuration child data resources, and MUST NOT be
   updated for changes to non-configuration child data resources.  Last-
   modified timestamps for data resources are discussed in Section 3.5.

   If the RESTCONF server is colocated with a NETCONF server, then the
   last-modified timestamp MUST represent the "running" datastore.

3.4.1.2.  Entity tag

   A unique opaque string is maintained and the "ETag" ([RFC7232],
   Section 2.3) 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 an entity tag for the top-level {+restconf}/
   data resource.  This entity tag is only affected by configuration
   data resources, and MUST NOT be updated for changes to non-
   configuration data.  Entity tags for data resources are discussed in
   Section 3.5.

   If the RESTCONF server is colocated with a NETCONF server, then this
   entity tag MUST represent the "running" datastore.

3.4.1.3.  Update Procedure






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   Changes to configuration data resources affect the timestamp and
   entity tag to that resource, any ancestor data resources, and the
   datastore resource.

   For example, an edit to disable an interface might be done by setting
   the leaf "/interfaces/interface/enabled" to "false".  The "enabled"
   data node and its ancestors (one "interface" list instance, and the
   "interfaces" container) are considered to be changed.  The datastore
   is considered to be changed when any top-level configuration data
   node is changed (e.g., "interfaces").

3.5.  Data Resource

   A data resource represents a YANG data node that is a descendant node
   of a datastore resource.  Each YANG-defined data node can be uniquely
   targeted by the request-line of an HTTP method.  Containers, leafs,
   leaf-list entries, list entries, anydata and anyxml nodes are data
   resources.

   The representation maintained for each data resource is the YANG
   defined subtree for that node.  HTTP methods on a data resource
   affect both the targeted data node and all its descendants, if any.

   A data resource can be retrieved with the GET method.  Data resources
   are accessed via the "{+restconf}/data" entry point.  This sub-tree
   is used to retrieve and edit data resources.  The fragment field in
   the request URI has no defined purpose if the target resource is a
   data resource.

   A configuration data resource can be altered by the client with some
   or all of the edit operations, depending on the target resource and
   the specific operation.  Refer to Section 4 for more details on edit
   operations.

3.5.1.  Timestamp

   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.

   The "Last-Modified" header information can be used by a RESTCONF
   client in subsequent requests, within the "If-Modified-Since" and
   "If-Unmodified-Since" headers.

   If maintained, the resource timestamp MUST be set to the current time
   whenever the resource or any configuration resource within the
   resource is altered.  If not maintained, then the resource timestamp
   for the datastore MUST be used instead.  If the RESTCONF server is



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   colocated with a NETCONF server, then the last-modified timestamp for
   a configuration data resource MUST represent the instance within the
   "running" datastore.

   This timestamp is only affected by configuration data resources, and
   MUST NOT be updated for changes to non-configuration data.

   For non-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.  The
   timestamps for non-configuration data resources are updated in an
   implementation-specific manner.

3.5.2.  Entity tag

   For configuration data resources, the server SHOULD maintain a
   resource entity tag for each 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.  If not maintained, then the resource entity tag
   for the datastore MUST be used instead.

   The "ETag" header information can be used by a RESTCONF client in
   subsequent requests, within the "If-Match" and "If-None-Match"
   headers.

   This entity tag is only affected by configuration data resources, and
   MUST NOT be updated for changes to non-configuration data.  If the
   RESTCONF server is colocated with a NETCONF server, then the entity
   tag for a configuration data resource MUST represent the instance
   within the "running" datastore.

   For non-configuration data resources, the server MAY maintain an
   entity tag for each resource, and return the "ETag" header when it is
   retrieved with the GET or HEAD methods.  The entity tags for non-
   configuration data resources are updated in an implementation-
   specific manner.

3.5.3.  Encoding Data Resource Identifiers in the Request URI

   In YANG, data nodes are identified with an absolute XPath expression,
   defined in [XPath], starting from the document root to the target
   resource.  In RESTCONF, URI-encoded path expressions are used
   instead.

   A predictable location for a data resource is important, since
   applications will code to the YANG data model module, which uses



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   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 3.5.3.1.  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 node in the
   path is defined in another module than its parent node, then module
   name followed by a colon character (":") is prepended to the node
   name in the resource identifier.  See Section 3.5.3.1 for details.

   If a data node in the path expression is a YANG leaf-list node, then
   the leaf-list value MUST be encoded according to the following rules:

   o  The identifier for the leaf-list MUST be encoded using one path
      segment [RFC3986].

   o  The path segment is constructed by having the leaf-list name,
      followed by an "=" character, followed by the leaf-list value.
      (e.g., /restconf/data/top-leaflist=fred).

   If a data node in the path expression is a YANG list node, then the
   key values for the list (if any) MUST be encoded according to the
   following rules:

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

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

   o  If there are multiple key leaf values, the path segment is
      constructed by having the list name, followed by the value of each
      leaf identified in the "key" statement, encoded in the order
      specified in the YANG "key" statement.  Each key leaf value except
      the last one is followed by a comma character.

   o  The key value is specified as a string, using the canonical
      representation for the YANG data type.  Any reserved characters
      MUST be percent-encoded, according to [RFC3986], section 2.1.

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






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   o  Since missing key values are not allowed, two consecutive commas
      are interpreted as a zero-length string.  (example:
      list=foo,,baz).

   o  The "list-instance" ABNF rule defined in Section 3.5.3.1
      represents the syntax of a list instance identifier.

   Resource URI values returned in Location headers for data resources
   MUST identify the module name as specified in
   [I-D.ietf-netmod-yang-json], 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:

   container top {
       list list1 {
           key "key1 key2 key3";
            ...
            list list2 {
                key "key4 key5";
                ...
                leaf X { type string; }
            }
        }
        leaf-list Y {
          type uint32;
        }
    }

   For the above YANG definition, the container "top" is defined in the
   "example-top" YANG module, and a target resource URI for leaf "X"
   would be encoded as follows (line wrapped for display purposes only):

    /restconf/data/example-top:top/list1=key1,key2,key3/
       list2=key4,key5/X

   For the above YANG definition, a target resource URI for leaf-list
   "Y" would be encoded as follows:

    /restconf/data/example-top:top/Y=instance-value

   The following example shows how reserved characters are percent-
   encoded within a key value.  The value of "key1" contains a comma,
   single-quote, double-quote, colon, double-quote, space, and forward
   slash. (,'":" /).  Note that double-quote is not a reserved
   characters and does not need to be percent-encoded.  The value of



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   "key2" is the empty string, and the value of "key3" is the string
   "foo".

   Example URL:

   /restconf/data/example-top:top/list1=%2C%27"%3A"%20%2F,,foo

3.5.3.1.  ABNF For Data Resource Identifiers

   The "api-path" Augmented Backus-Naur Form (ABNF) syntax is used to
   construct RESTCONF path identifiers:

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

       api-identifier = [module-name ":"] identifier   ;; note 1

       module-name = identifier

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

       key-value = string      ;; note 1

       string = <a quoted or unquoted string>

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

   Note 1: The syntax for "api-identifier" and "key-value" MUST conform
   to the JSON identifier encoding rules in Section 4 of
   [I-D.ietf-netmod-yang-json].

3.5.4.  Defaults Handling

   RESTCONF requires that a server report its default handling mode (see
   Section 9.1.2 for details).  If the optional "with-defaults" query
   parameter is supported by the server, a client may use it to control
   retrieval of default values (see Section 4.8.9 for details).

   If a leaf or leaf-list is missing from the configuration and there is
   a YANG-defined default for that data resource, then the server MUST
   use the YANG-defined default as the configured value.

   If the target of a GET method is a data node that represents a leaf
   or leaf-list that has a default value, and the leaf or leaf-list has



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   not been instantiated yet, the server MUST return the default
   value(s) that are in use by the server.  In this case, the server
   MUST ignore its basic-mode, described in Section 4.8.9, and return
   the default value.

   If the target of a GET method is a data node that represents a
   container or list that has any child resources with default values,
   for the child resources that have not been given value yet, the
   server MAY return the default values that are in use by the server,
   in accordance with its reported default handing mode and query
   parameters passed by the client.

3.6.  Operation Resource

   An operation resource represents an RPC operation defined with the
   YANG "rpc" statement or a data-model specific action defined with a
   YANG "action" statement.  It is invoked using a POST method on the
   operation resource.  The fragment field in the request URI has no
   defined purpose if the target resource is an operation resource.

   An RPC operation is invoked as:

   POST {+restconf}/operations/<operation>

   The <operation> field identifies the module name and rpc identifier
   string for the desired operation.

   For example, if "module-A" defined a "reset" rpc 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

   An action is invoked as:

   POST {+restconf}/data/<data-resource-identifier>/<action>

   where <data-resource-identifier> contains the path to the data node
   where the action is defined, and <action> is the name of the action.

   For example, if "module-A" defined a "reset-all" action in the
   container "interfaces", then invoking this action would be requested
   as follows:

   POST /restconf/data/module-A:interfaces/reset-all HTTP/1.1
   Server: example.com





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   If the "rpc" or "action" statement has an "input" section then
   instances of these input parameters are encoded in the module
   namespace where the "rpc" or "action" statement is defined, in an XML
   element or JSON object named "input", which is in the module
   namespace where the "rpc" or "action" statement is defined.

   If the "rpc" or "action" statement has an "input" section and the
   "input" object tree contains any child data nodes which are
   considered mandatory nodes, then a message-body MUST be sent by the
   client in the request.

   If the "rpc" or "action" statement has an "input" section and the
   "input" object tree does not contain any child nodes which are
   considered mandatory nodes, then a message-body MAY be sent by the
   client in the request.

   If the "rpc" or "action" statement has no "input" section, the
   request message MUST NOT include a message-body.

   If the "rpc" or "action" statement has an "output" section then
   instances of these output parameters are encoded in the module
   namespace where the "rpc" or "action" statement is defined, in an XML
   element or JSON object named "output", which is in the module
   namespace where the "rpc" or "action" statement is defined.

   If the RPC operation is invoked without errors, and if the "rpc" or
   "action" statement has an "output" section and the "output" object
   tree contains any child data nodes which are considered mandatory
   nodes, then a response message-body MUST be sent by the server in the
   response.

   If the RPC operation is invoked without errors, and if the "rpc" or
   "action" statement has an "output" section and the "output" object
   tree does not contain any child nodes which are considered mandatory
   nodes, then a response message-body MAY be sent by the server in the
   response.

   If the RPC operation is invoked without errors, and if the "rpc" or
   "action" statement has no "output" section, the response message MUST
   NOT include a message-body, and MUST send a "204 No Content" status-
   line instead.

   If the RPC operation input is not valid, or the RPC operation is
   invoked but errors occur, then a message-body MUST be sent by the
   server, containing an "errors" resource, as defined in Section 3.9.
   A detailed example of an operation resource error response can be
   found in Section 3.6.3.




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   All operation resources representing RPC operations supported by the
   server MUST be identified in the {+restconf}/operations subtree
   defined in Section 3.3.2.  Operation resources representing YANG
   actions are not identified in this subtree since they are invoked
   using a URI within the {+restconf}/data subtree.

3.6.1.  Encoding Operation Resource Input Parameters

   If the "rpc" or "action" 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.  The
   "input" node is defined to be in the namespace of the module
   containing the "rpc" or "action" statement.

   Examples:

   The following YANG module is used for the RPC operation examples in
   this section.

   module example-ops {
     namespace "https://example.com/ns/example-ops";
     prefix "ops";

     organization "Example, Inc.";
     contact "support at example.com";
     description "Example Operations Data Model Module";
     revision "2016-07-07" {
       description "Initial version.";
       reference "example.com document 3-3373";
     }


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

     rpc get-reboot-info {
       output {
         leaf reboot-time {
           units seconds;



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           type uint32;
         }
         leaf message { type string; }
         leaf language { type string; }
       }
     }
   }


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

   module example-actions {
     yang-version 1.1;
     namespace "https://example.com/ns/example-actions";
     prefix "act";
     import ietf-yang-types { prefix yang; }

     organization "Example, Inc.";
     contact "support at example.com";
     description "Example Actions Data Model Module";
     revision "2016-07-07" {
       description "Initial version.";
       reference "example.com document 2-9973";
     }

     revision "2016-03-10";

     container interfaces {
       list interface {
         key name;
         leaf name { type string; }

         action reset {
           input {
             leaf delay {
               units seconds;
               type uint32;
               default 0;
             }
           }
         }

         action get-last-reset-time {
           output {
             leaf last-reset {
               type yang:date-and-time;
               mandatory true;



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             }
           }
         }
       }
     }

   }


   RPC Input Example:

   The client might send the following POST request message to invoke
   the "reboot" RPC operation:

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

   <input xmlns="https://example.com/ns/example-ops">
    <delay>600</delay>
    <message>Going down for system maintenance</message>
    <language>en-US</language>
   </input>

   The server might respond:

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

   The same example request message is shown here using JSON encoding:

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

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

   Action Input Example:

   The client might send the following POST request message to invoke
   the "reset" action (text wrap for display purposes):



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   POST /restconf/data/example-actions:interfaces/interface=eth0
     /reset HTTP/1.1
   Host: example.com
   Content-Type: application/yang-data

   <input xmlns="https://example.com/ns/example-actions">
     <delay>600</delay>
   </input>

   The server might respond:

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

   The same example request message is shown here using JSON encoding
   (text wrap for display purposes):

      POST /restconf/data/example-actions:interfaces/interface=eth0
        /reset HTTP/1.1
      Host: example.com
      Content-Type: application/yang-data+json

      { "example-actions:input" : {
          "delay" : 600
        }
      }

3.6.2.  Encoding Operation Resource Output Parameters

   If the "rpc" or "action" 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.  The
   "output" node is defined to be in the namespace of the module
   containing the "rpc" or "action" statement.

   The request URI is not returned in the response.  This URI might have
   context information required to associate the output to the specific
   "rpc" or "action" statement used in the request.

   Examples:

   RPC Output Example:

   The "example-ops" YANG module defined in Section 3.6.1 is used for
   this example.





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   The client might send the following POST request message to invoke
   the "get-reboot-info" operation:

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

   The server might respond:

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

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

   The same response is shown here using XML encoding:

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

   <output xmlns="https://example.com/ns/example-ops">
     <reboot-time>30</reboot-time>
     <message>Going down for system maintenance</message>
     <language>en-US</language>
   </output>

   Action Output Example:

   The "example-actions" YANG module defined in Section 3.6.1 is used
   for this example.

   The client might send the following POST request message to invoke
   the "get-last-reset-time" action:

   POST /restconf/data/example-actions:interfaces/interface=eth0
      /get-last-reset-time HTTP/1.1
   Host: example.com
   Accept: application/yang-data+json




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   The server might respond:

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

      {
        "example-actions:output" : {
          "last-reset" : "2015-10-10T02:14:11Z"
        }
      }

3.6.3.  Encoding Operation Resource Errors

   If any errors occur while attempting to invoke the operation or
   action, then an "errors" media type is returned with the appropriate
   error status.

   Using the "reboot" RPC operation from the example in Section 3.6.1,
   the client might send the following POST request message:

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

   <input xmlns="https://example.com/ns/example-ops">
     <delay>-33</delay>
     <message>Going down for system maintenance</message>
     <language>en-US</language>
   </input>

   The server might respond with an "invalid-value" error:

   HTTP/1.1 400 Bad Request
   Date: Mon, 25 Apr 2012 11:10:30 GMT
   Server: example-server
   Content-Type: application/yang-data













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   <errors xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
     <error>
       <error-type>protocol</error-type>
       <error-tag>invalid-value</error-tag>
       <error-path xmlns:ops="https://example.com/ns/example-ops">
         /ops:input/ops:delay
       </error-path>
       <error-message>Invalid input parameter</error-message>
     </error>
   </errors>

   The same response is shown here in JSON encoding:

      HTTP/1.1 400 Bad Request
      Date: Mon, 25 Apr 2012 11:10:30 GMT
      Server: example-server
      Content-Type: application/yang-data+json

      { "ietf-restconf:errors" : {
          "error" : [
            {
              "error-type" : "protocol",
              "error-tag" : "invalid-value",
              "error-path" : "/example-ops:input/delay",
              "error-message" : "Invalid input parameter",
            }
          ]
        }
      }

3.7.  Schema Resource

   The server can optionally support retrieval of the YANG modules it
   supports.  If retrieval is supported, then the "schema" leaf MUST be
   present in the associated "module" list entry, defined in
   [I-D.ietf-netconf-yang-library].

   To retrieve a YANG module, a client first needs to get the URL for
   retrieving the schema, which is stored in the "schema" leaf.  Note
   that there is no required structure for this URL.  The URL value
   shown below is just an example.

   The client might send the following GET request message:

   GET /restconf/data/ietf-yang-library:modules-state/module=
       example-jukebox,2015-04-04/schema HTTP/1.1
   Host: example.com
   Accept: application/yang-data+json



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   The server might respond:

      HTTP/1.1 200 OK
      Date: Thu, 11 Feb 2016 11:10:30 GMT
      Server: example-server
      Content-Type: application/yang-data+json

      {
        "ietf-yang-library:schema":
         "https://example.com/mymodules/example-jukebox/2015-04-04"
      }

   Next the client needs to retrieve the actual YANG schema.

   The client might send the following GET request message:

   GET https://example.com/mymodules/example-jukebox/2015-04-04
      HTTP/1.1
   Host: example.com
   Accept: application/yang

   The server might respond:

      HTTP/1.1 200 OK
      Date: Thu, 11 Feb 2016 11:10:31 GMT
      Server: example-server
      Content-Type: application/yang

      module example-jukebox {

         // contents of YANG module deleted for this example...

      }

3.8.  Event Stream Resource

   An "event 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 6.3.

   A notification stream functions according to the NETCONF
   Notifications specification [RFC5277].  The available streams can be
   retrieved from the stream list, which specifies the syntax and
   semantics of a stream resource.





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   The fragment field in the request URI has no defined purpose if the
   target resource is an event stream resource.

3.9.  Errors YANG Data Template

   An "errors" YANG data template models 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.  It
   is not considered a resource type because no instances can be
   retrieved with a GET request.

   The "ietf-restconf" YANG module contains the "yang-errors" YANG data
   template, that specifies the syntax and semantics of an "errors"
   container within a RESTCONF response.  RESTCONF error handling
   behavior is defined in Section 7.

4.  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 and edit operations, which are identified
   with the NETCONF "nc:operation" attribute.

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

                         CRUD Methods in RESTCONF

   The "remove" operation attribute for the NETCONF <edit-config>
   operation 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 when using a plain patch (see
   Section 4.6.1); other media-types may provide more granular control.

   Access control mechanisms MUST be used to limit what operations can
   be used.  In particular, RESTCONF is compatible with the NETCONF



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   Access Control Model (NACM) [RFC6536], as there is a specific mapping
   between RESTCONF and NETCONF operations, defined in Section 4.  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
   [RFC7231].  This section defines the RESTCONF protocol usage for each
   HTTP method.

4.1.  OPTIONS

   The OPTIONS method is sent by the client to discover which methods
   are supported by the server for a specific resource (e.g., GET, POST,
   DELETE, etc.).  The server MUST implement this method.

   If the PATCH method is supported, then the "Accept-Patch" header MUST
   be supported and returned in the response to the OPTIONS request, as
   defined in [RFC5789].

4.2.  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 message-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.  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 message-body is
   included.

4.3.  GET

   The GET method is sent by the client to retrieve data and metadata
   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.

   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 the



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   target resource, an error response containing a "401 Unauthorized"
   status-line SHOULD be returned.  A server MAY return a "404 Not
   Found" status-line, as described in section 6.5.3 in [RFC7231].

   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.

   If any content is returned to the client, then the server MUST send a
   valid response message-body.  More than one element MUST NOT be
   returned for XML encoding.

   If a retrieval request for a data resource representing a YANG leaf-
   list or list object identifies more than one instance, and XML
   encoding is used in the response, then an error response containing a
   "400 Bad Request" status-line MUST be returned by the server.

   If a retrieval request for a data resource represents an instance
   that does not exist, then an error response containing a "404 Not
   Found" status-line MUST be returned by the server.

   If the target resource of a retrieval request is for an operation
   resource then a "405 Method Not Allowed" status-line MUST be returned
   by the server.

   Note that the way that access control is applied to data resources
   may not be completely compatible with HTTP caching.  The Last-
   Modified and ETag headers maintained for a data resource are not
   affected by changes to the access control rules for that data
   resource.  It is possible for the representation of a data resource
   that is visible to a particular client to be changed without
   detection via the Last-Modified or ETag values.

   Example:

   The client might request the response headers for an XML
   representation of the a specific "album" resource:

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

   The server might respond:

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



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   Content-Type: application/yang-data
   Cache-Control: no-cache
   ETag: "a74eefc993a2b"
   Last-Modified: Mon, 23 Apr 2012 11:02:14 GMT

   <album xmlns="http://example.com/ns/example-jukebox"
          xmlns:jbox="http://example.com/ns/example-jukebox">
     <name>Wasting Light</name>
     <genre>jbox:alternative</genre>
     <year>2011</year>
   </album>

4.4.  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 child resource     |
      | Operation | Invoke an RPC operation                        |
      +-----------+------------------------------------------------+

                     Resource Types that Support POST

4.4.1.  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 top-level resource or child
   resource, respectively.  The message-body is expected to contain the
   content of a child resource to create within the parent (target
   resource).  The message-body MUST contain exactly one instance of the
   expected data resource.  The data-model for the child tree is the
   subtree as defined by YANG for the child resource.

   The "insert" Section 4.8.5 and "point" Section 4.8.6 query parameters
   MUST be supported by the POST method for datastore and data
   resources.  These parameters are only allowed if the list or leaf-
   list is ordered-by user.

   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.




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   If the data resource already exists, then the POST request MUST fail
   and a "409 Conflict" status-line MUST be returned.

   If the user is not authorized to create the target resource, an error
   response containing a "403 Forbidden" status-line SHOULD be returned.
   A server MAY return a "404 Not Found" status-line, as described in
   section 6.5.3 in [RFC7231].  All other error responses are handled
   according to the procedures defined in Section 7.

   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" : {} }

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

   HTTP/1.1 201 Created
   Date: Mon, 23 Apr 2012 17:01:00 GMT
   Server: example-server
   Location: https://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.

4.4.2.  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 3.6 for details on operation resources.

   If the POST 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" status-line is returned
   to the client.  All other error responses are handled according to
   the procedures defined in Section 7.



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   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-data+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

4.5.  PUT

   The PUT method is sent by the client to create or replace the target
   data resource.  A request message-body MUST be present, representing
   the new data resource, or the server MUST return "400 Bad Request"
   status-line.

   The only target resource media type that supports PUT is the data
   resource.  The message-body is expected to contain the content used
   to create or replace the target resource.

   The "insert" (Section 4.8.5) and "point" (Section 4.8.6) query
   parameters MUST be supported by the PUT method for data resources.
   These parameters are only allowed if the list or leaf-list is
   ordered-by user.

   Consistent with [RFC7231], if the PUT request creates a new resource,
   a "201 Created" status-line is returned.  If an existing resource is
   modified, a "204 No Content" status-line is returned.

   If the user is not authorized to create or replace the target
   resource an error response containing a "403 Forbidden" status-line
   SHOULD be returned.  A server MAY return a "404 Not Found" status-
   line, as described in section 6.5.3 in [RFC7231].  All other error



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   responses are handled according to the procedures defined in
   Section 7.

   If the target resource represents a YANG leaf-list, then the PUT
   method MUST NOT change the value of the leaf-list instance.

   If the target resource represents a YANG list instance, then the PUT
   method MUST NOT change any key leaf values in the message-body
   representation.

   Example:

   An "album" 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-line is wrapped for display purposes
   only:

      PUT /restconf/data/example-jukebox:jukebox/
          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"

   The same request is shown here using XML encoding:

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



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   <album xmlns="http://example.com/ns/example-jukebox"
          xmlns:jbox="http://example.com/ns/example-jukebox">
     <name>Wasting Light</name>
     <genre>jbox:alternative</genre>
     <year>2011</year>
   </album>

4.6.  PATCH

   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 mechanism needs a
   unique media type.  Zero or more patch media types MAY be supported
   by the server.  The media types supported by a server can be
   discovered by the client by sending an OPTIONS request, and examining
   the Accept-Patch header field in the response.  (see Section 4.1).

   This document defines one patch mechanism (Section 4.6.1).  Another
   patch mechanism, the YANG PATCH mechanism, is defined in
   [I-D.ietf-netconf-yang-patch].  Other patch mechanisms may be defined
   by future specifications.

   If the target resource instance does not exist, the server MUST NOT
   create it.

   If the PATCH 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" status-line SHOULD be returned.
   A server MAY return a "404 Not Found" status-line, as described in
   section 6.5.3 in [RFC7231].  All other error responses are handled
   according to the procedures defined in Section 7.

4.6.1.  Plain Patch

   The plain patch mechanism merges the contents of the message-body
   with the target resource.  The message-body for a plain patch MUST be
   present and MUST be represented by the media type "application/
   yang-data" or "application/yang-data+json".

   Plain patch can be used to create or update, but not delete, a child
   resource within the target resource.  Please see
   [I-D.ietf-netconf-yang-patch] for an alternate media-type supporting
   the ability to delete child resources.  The YANG Patch Media Type
   allows multiple sub-operations (e.g., merge, delete) within a single
   PATCH operation.



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   If the target resource represents a YANG leaf-list, then the PATCH
   method MUST NOT change the value of the leaf-list instance.

   If the target resource represents a YANG list instance, then the
   PATCH method MUST NOT change any key leaf values in the message-body
   representation.

   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-line is wrapped
   for display purposes only:

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

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

   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"

4.7.  DELETE

   The DELETE method is used to delete the target resource.  If the
   DELETE request succeeds, a "204 No Content" status-line is returned.

   If the user is not authorized to delete the target resource then an
   error response containing a "403 Forbidden" status-line SHOULD be
   returned.  A server MAY return a "404 Not Found" status-line, as
   described in section 6.5.3 in [RFC7231].  All other error responses
   are handled according to the procedures defined in Section 7.

   If the target resource represents a YANG leaf-list or list, then the
   DELETE method SHOULD NOT delete more than one such instance.  The
   server MAY delete more than one instance if a query parameter is used
   requesting this behavior.  (Definition of this query parameter is
   outside the scope of this document.)



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   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 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

4.8.  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.

   o  Query parameters can be given in any order.

   o  Each parameter can appear at most once in a request URI.

   o  If more than one instance of a query parameter is present, then a
      "400 Bad Request" status-line MUST be returned by the server.

   o  A default value may apply if the parameter is missing.

   o  Query parameter names and values are case-sensitive

   o  A server MUST return an error with a '400 Bad Request' status-line
      if a query parameter is unexpected.

   +-------------------+-------------+---------------------------------+
   | Name              | Methods     | Description                     |
   +-------------------+-------------+---------------------------------+
   | content           | GET, HEAD   | Select config and/or non-config |
   |                   |             | data resources                  |
   | depth             | GET, HEAD   | Request limited sub-tree depth  |
   |                   |             | in the reply content            |
   | fields            | GET, HEAD   | Request a subset of the target  |
   |                   |             | resource contents               |
   | filter            | GET, HEAD   | Boolean notification filter for |
   |                   |             | event stream resources          |
   | insert            | POST, PUT   | Insertion mode for ordered-by   |



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   |                   |             | user data resources             |
   | point             | POST, PUT   | Insertion point for ordered-by  |
   |                   |             | user data resources             |
   | start-time        | GET, HEAD   | Replay buffer start time for    |
   |                   |             | event stream resources          |
   | stop-time         | GET, HEAD   | Replay buffer stop time for     |
   |                   |             | event stream resources          |
   | with-defaults     | GET, HEAD   | Control retrieval of default    |
   |                   |             | values                          |
   +-------------------+-------------+---------------------------------+

                         RESTCONF Query Parameters

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

   If vendors define additional query parameters, they SHOULD use a
   prefix (such as the enterprise or organization name) for query
   parameter names in order to avoid collisions with other parameters.

4.8.1.  The "content" Query Parameter

   The "content" parameter controls how descendant nodes of the
   requested data nodes will be processed in the reply.

   The allowed values are:

    +-----------+-----------------------------------------------------+
    | Value     | Description                                         |
    +-----------+-----------------------------------------------------+
    | config    | Return only configuration descendant data nodes     |
    | nonconfig | Return only non-configuration descendant data nodes |
    | all       | Return all descendant data nodes                    |
    +-----------+-----------------------------------------------------+

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

   If this query parameter is not present, the default value is "all".
   This query parameter MUST be supported by the server.

4.8.2.  The "depth" Query Parameter

   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.  If the "fields"
   parameter (Section 4.8.3) is used to select descendant data nodes,
   these nodes all have a depth value of 1.  This has the effect of



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   including the nodes specified by the fields, even if the "depth"
   value is less than the actual depth level of the specified fields.
   Any child nodes which are contained within a parent node have a depth
   value that is 1 greater than its parent.

   The value of the "depth" parameter is either an integer between 1 and
   65535, or the string "unbounded".  "unbounded" is the default.

   This parameter is only allowed for GET methods on API, datastore, and
   data resources.  A "400 Bad Request" status-line is returned if it
   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.  The exception is the datastore resource.  If
   this resource type is retrieved then by default the datastore and all
   child data resources are returned.

   If the "depth" query parameter URI is listed in the "capability"
   leaf-list in Section 9.3, then the server supports the "depth" query
   parameter.

4.8.3.  The "fields" Query Parameter

   The "fields" query parameter is used to optionally identify data
   nodes within the target resource to be retrieved in a GET method.
   The client can use this parameter to retrieve a subset of all nodes
   in a resource.

   A value of the "fields" query parameter matches the following rule:

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

   "api-identifier" is defined in Section 3.5.3.1.

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

   Parentheses are used to specify sub-selectors of a node.  Note that
   there is no path separator character '/' between a "path" field and
   left parenthesis character '('.







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   For example, assume the target resource is the "album" list.  To
   retrieve only the "label" and "catalogue-number" of the "admin"
   container within an album, use:
   "fields=admin(label;catalogue-number)".

   "/" is used in a path to retrieve a child node of a node.  For
   example, to retrieve only the "label" of an album, use: "fields=admin
   /label".

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

   If the "fields" query parameter URI is listed in the "capability"
   leaf-list in Section 9.3, then the server supports the "fields"
   parameter.

4.8.4.  The "filter" Query Parameter

   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" status-line is returned if used
   for other methods or resource types.

   The format of this parameter is an XPath 1.0 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
      1.0, plus any functions defined by the data model.

   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 event notification
   is delivered to the client.





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   If the "filter" query parameter URI is listed in the "capability"
   leaf-list in Section 9.3, then the server supports the "filter" query
   parameter.

4.8.5.  The "insert" Query Parameter

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

   The allowed values are:

   +-----------+-------------------------------------------------------+
   | Value     | Description                                           |
   +-----------+-------------------------------------------------------+
   | first     | Insert the new data as the new first entry.           |
   | last      | Insert the new data as the new last entry.            |
   | before    | Insert the new data before the insertion point, as    |
   |           | specified by the value of the "point" parameter.      |
   | after     | Insert the new data after the insertion point, as     |
   |           | specified by the value of the "point" parameter.      |
   +-----------+-------------------------------------------------------+

   The default value is "last".

   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
   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" status-line is returned.

   The "insert" query parameter MUST be supported by the server.

4.8.6.  The "point" Query Parameter

   The "point" parameter is used to specify the insertion point for a
   data resource that is being created or moved within an ordered-by
   user list or leaf-list.

   The value of the "point" parameter is a string that identifies the
   path to the insertion point object.  The format is the same as a
   target resource URI string.







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   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
   user.

   If the "insert" query parameter is not present, or has a value other
   than "before" or "after", then a "400 Bad Request" status-line is
   returned.

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

   The "point" query parameter MUST be supported by the server.

4.8.7.  The "start-time" Query Parameter

   The "start-time" parameter is used to trigger the notification replay
   feature defined in [RFC5277] 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 stream list entry for
   the stream resource, then the server MUST return a "400 Bad Request"
   status-line.

   The value of the "start-time" parameter is of type "date-and-time",
   defined in the "ietf-yang" YANG module [RFC6991].

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

   If this parameter is not present, then a replay subscription is not
   being 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.  A client can obtain a server's current time
   by examining the "Date" header field that the server returns in
   response messages, according to [RFC7231].

   If this query parameter is supported by the server, then the "replay"
   query parameter URI MUST be listed in the "capability" leaf-list in
   Section 9.3.  The "stop-time" query parameter MUST also be supported
   by the server.

   If the "replay-support" leaf has the value 'true' in the "stream"
   entry (defined in Section 9.3) then the server MUST support the
   "start-time" and "stop-time" query parameters for that stream.





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4.8.8.  The "stop-time" Query Parameter

   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.

   The value of the "stop-time" parameter is of type "date-and-time",
   defined in the "ietf-yang" YANG module [RFC6991].

   This parameter is only allowed for GET methods on a text/event-stream
   data resource.  A "400 Bad Request" status-line 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.

   If this query parameter is supported by the server, then the "replay"
   query parameter URI MUST be listed in the "capability" leaf-list in
   Section 9.3.  The "start-time" query parameter MUST also be supported
   by the server.

   If the "replay-support" leaf is present in the "stream" entry
   (defined in Section 9.3) then the server MUST support the
   "start-time" and "stop-time" query parameters for that stream.

4.8.9.  The "with-defaults" Query Parameter

   The "with-defaults" parameter is used to specify how information
   about default data nodes should be returned in response to GET
   requests on data resources.

   If the server supports this capability, then it MUST implement the
   behavior in Section 4.5.1 of [RFC6243], except applied to the
   RESTCONF GET operation, instead of the NETCONF operations.

   +---------------------------+---------------------------------------+
   | Value                     | Description                           |
   +---------------------------+---------------------------------------+
   | report-all                | All data nodes are reported           |
   | trim                      | Data nodes set to the YANG default    |
   |                           | are not reported                      |
   | explicit                  | Data nodes set to the YANG default by |
   |                           | the client are reported               |
   | report-all-tagged         | All data nodes are reported and       |
   |                           | defaults are tagged                   |
   +---------------------------+---------------------------------------+




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   If the "with-defaults" parameter is set to "report-all" then the
   server MUST adhere to the defaults reporting behavior defined in
   Section 3.1 of [RFC6243].

   If the "with-defaults" parameter is set to "trim" then the server
   MUST adhere to the defaults reporting behavior defined in Section 3.2
   of [RFC6243].

   If the "with-defaults" parameter is set to "explicit" then the server
   MUST adhere to the defaults reporting behavior defined in Section 3.3
   of [RFC6243].

   If the "with-defaults" parameter is set to "report-all-tagged" then
   the server MUST adhere to the defaults reporting behavior defined in
   Section 3.4 of [RFC6243].

   If the "with-defaults" parameter is not present then the server MUST
   adhere to the defaults reporting behavior defined in its "basic-mode"
   parameter for the "defaults" protocol capability URI, defined in
   Section 9.1.2.

   If the server includes the "with-defaults" query parameter URI in the
   "capability" leaf-list in Section 9.3, then the "with-defaults" query
   parameter MUST be supported.

5.  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.

5.1.  Request URI Structure

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

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

        <OP> /<restconf>/<path>?<query>#<fragment>

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

          M       M        O        O         I



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       M=mandatory, O=optional, I=ignored

       where:

      <OP> is the HTTP method
      <restconf> is the RESTCONF entry point
      <path> is the Target Resource URI
      <query> is the query parameter list
      <fragment> is not used in RESTCONF

   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 4.

   o  entry: the root of the RESTCONF API configured on this HTTP
      server, discovered by getting the "/.well-known/host-meta"
      resource, as described in Section 3.1.

   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
      YANG data template named "yang-api", found in Section 8.

   o  query: the set of parameters associated with the RESTCONF message,
      as defined in section 3.4 of [RFC3986].  RESTCONF parameters have
      the familiar form of "name=value" pairs.  Most query parameters
      are optional to implement by the server and optional to use by the
      client.  Each optional query parameter is identified by a URI.
      The server MUST list the optional query parameter URIs it supports
      in the "capabilities" list defined in Section 9.3.

   There is a specific set of parameters defined, although the server
   MAY choose to support query parameters not defined in this document.
   The contents of the any query parameter value MUST be encoded
   according to [RFC3986], Section 3.4.  Any reserved characters MUST be
   percent-encoded, according to [RFC3986], section 2.1.

   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 uses 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.




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   Refer to Appendix D for examples of RESTCONF Request URIs.

5.2.  Message Encoding

   RESTCONF messages are encoded in HTTP according to [RFC7230].  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.  A server MUST
   support XML or JSON encoding.  XML encoding rules for data nodes are
   defined in [I-D.ietf-netmod-rfc6020bis].  The same encoding rules are
   used for all XML content.  JSON encoding rules are defined in
   [I-D.ietf-netmod-yang-json].  JSON encoding of metadata is defined in
   [I-D.ietf-netmod-yang-metadata].  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.

   The server MUST support the "Accept" header and "406 Not Acceptable"
   status-line, as defined in [RFC7231].  Response output content
   encoding format is identified with the Accept header in the request.
   If it is not specified, the request input encoding format SHOULD be
   used, or the server MAY choose any supported content encoding format.

   If there was no request input, then the default output encoding is
   XML or JSON, depending on server preference.  File extensions encoded
   in the request are not used to identify format encoding.

   A client can determine if the RESTCONF server supports an encoding
   format by sending a request using a specific format in the Content-
   Type and/or Accept header.  If the server does not support the
   requested input encoding for a request, then it MUST return an error
   response with a '415 Unsupported Media Type' status-line.  If the
   server does not support any of the requested output encodings for a
   request, then it MUST return an error response with a '406 Not
   Acceptable' status-line.

5.3.  RESTCONF Metadata

   The RESTCONF protocol needs to retrieve the same metadata 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.





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   With the XML encoding, the metadata is encoded as attributes in XML.
   With the JSON encoding, the metadata is encoded as specified in
   [I-D.ietf-netmod-yang-metadata].

   The following examples are based on the example in Appendix D.3.9.
   The "report-all-tagged" mode for the "with-defaults" query parameter
   requires that a "default" attribute be returned for default nodes.
   This example shows that attribute for the "mtu" leaf .

5.3.1.  XML MetaData Encoding Example

   GET /restconf/data/interfaces/interface=eth1
       ?with-defaults=report-all-tagged HTTP/1.1
   Host: example.com
   Accept: application/yang-data

   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

   <interface
     xmlns="urn:example.com:params:xml:ns:yang:example-interface">
     <name>eth1</name>
     <mtu xmlns:wd="urn:ietf:params:xml:ns:netconf:default:1.0"
       wd:default="true">1500</mtu>
     <status>up</status>
   </interface>

5.3.2.  JSON MetaData Encoding Example

   Note that RFC 6243 defines the "default" attribute with XSD, not
   YANG, so the YANG module name has to be assigned instead of derived
   from the YANG module name.  The value "ietf-netconf-with-defaults" is
   assigned for JSON metadata encoding.

   GET /restconf/data/interfaces/interface=eth1
       ?with-defaults=report-all-tagged 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



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      Content-Type: application/yang-data+json

      {
        "example:interface": [
          {
            "name" : "eth1",
            "mtu" : 1500,
            "@mtu": {
               "ietf-netconf-with-defaults:default" : true
            },
            "status" : "up"
          }
        ]
      }

5.4.  Return Status

   Each message represents some sort of resource access.  An HTTP
   "status-line" header line is returned for each request.  If a "4xx"
   range status code is returned in the status-line, then the error
   information SHOULD be returned in the response, according to the
   format defined in Section 7.1.  If a "5xx" range status code is
   returned in the status-line, then the error information MAY be
   returned in the response, according to the format defined in
   Section 7.1.  If a 1xx, 2xx, or 3xx range status code is returned in
   the status-line, then error information MUST NOT be returned in the
   response, since these ranges do not represent error conditions.

5.5.  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.

   Instead of relying on 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 metadata is maintained for the target resource.

6.  Notifications




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   The RESTCONF protocol supports YANG-defined event notifications.  The
   solution preserves aspects of NETCONF Event Notifications [RFC5277]
   while utilizing the Server-Sent Events [W3C.REC-eventsource-20150203]
   transport strategy.

6.1.  Server Support

   A RESTCONF server MAY support RESTCONF notifications.  Clients may
   determine if a server supports RESTCONF notifications by using the
   HTTP operation OPTIONS, HEAD, or GET on the stream list.  The server
   does not support RESTCONF notifications if an HTTP error code is
   returned (e.g., "404 Not Found" status-line).

6.2.  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 stream list.

   The "restconf-state/streams" container definition in the
   "ietf-restconf-monitoring" module (defined in Section 9.3) is used to
   specify the structure and syntax of the conceptual child resources
   within the "streams" resource.

   For example:

   The client might send the following request:

   GET /restconf/data/ietf-restconf-monitoring:restconf-state/
       streams HTTP/1.1
   Host: example.com
   Accept: application/yang-data

   The server might send the following response:

   HTTP/1.1 200 OK
   Content-Type: application/yang-data

   <streams
     xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring">
      <stream>
         <name>NETCONF</name>
         <description>default NETCONF event stream
         </description>
         <replay-support>true</replay-support>
         <replay-log-creation-time>
            2007-07-08T00:00:00Z



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         </replay-log-creation-time>
         <access>
            <encoding>xml</encoding>
            <location>https://example.com/streams/NETCONF
            </location>
         </access>
         <access>
            <encoding>json</encoding>
            <location>https://example.com/streams/NETCONF-JSON
            </location>
         </access>
      </stream>
      <stream>
         <name>SNMP</name>
         <description>SNMP notifications</description>
         <replay-support>false</replay-support>
         <access>
            <encoding>xml</encoding>
            <location>https://example.com/streams/SNMP</location>
         </access>
      </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>
         <access>
            <encoding>xml</encoding>
            <location>
              https://example.com/streams/syslog-critical
            </location>
         </access>
      </stream>
   </streams>

6.3.  Subscribing to Receive Notifications

   RESTCONF clients can determine the URL for the subscription resource
   (to receive notifications) by sending an HTTP GET request for the
   "location" leaf with the stream list entry.  The value returned by
   the server can be used for the actual notification subscription.

   The client will send an HTTP GET request for the URL returned by the
   server with the "Accept" type "text/event-stream".




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   The server will treat the connection as an event stream, using the
   Server Sent Events [W3C.REC-eventsource-20150203] 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:

   The client might send the following request:

   GET /restconf/data/ietf-restconf-monitoring:restconf-state/
       streams/stream=NETCONF/access=xml/location HTTP/1.1
   Host: example.com
   Accept: application/yang-data

   The server might send the following response:

   HTTP/1.1 200 OK
   Content-Type: application/yang-data

   <location
     xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring">
     https://example.com/streams/NETCONF
   </location>

   The RESTCONF client can then use this URL value to start monitoring
   the event stream:

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

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

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

6.3.1.  NETCONF Event Stream

   The server SHOULD support the "NETCONF" notification stream defined
   in [RFC5277].  For this stream, RESTCONF notification subscription



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   requests MAY specify parameters indicating the events it wishes to
   receive.  These query parameters are optional to implement, and only
   available if the server supports them.

            +------------+---------+-------------------------+
            | Name       | Section | Description             |
            +------------+---------+-------------------------+
            | start-time | 4.8.7   | replay event start time |
            | stop-time  | 4.8.8   | replay event stop time  |
            | filter     | 4.8.4   | boolean content filter  |
            +------------+---------+-------------------------+

                      NETCONF Stream Query Parameters

   The semantics and syntax for these query parameters are defined in
   the sections listed above.  The YANG definition MUST be converted to
   a URI-encoded string for use in the request URI.

   Refer to Appendix D.3.6 for filter parameter examples.

6.4.  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
   schema for the "notification" element in Section 4 of [RFC5277],
   except the XML namespace for this element is defined as:

   urn:ietf:params:xml:ns:yang:ietf-restconf

   For JSON encoding purposes, the module name for the "notification"
   element is "ietf-restconf".

   Two child nodes within the "notification" container are expected,
   representing the event time and the event payload.  The "event-time"
   node is defined within the "ietf-restconf" module namespace.  The
   name and namespace of the payload element are determined by the YANG
   module containing the notification-stmt.

   In the following example, the YANG module "example-mod" is used:

     module example-mod {
       namespace "http://example.com/event/1.0";
       prefix ex;




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       notification event {
        leaf event-class { type string; }
        container reporting-entity {
          leaf card { type string; }
        }
        leaf severity { type string; }
       }
     }

   An example SSE event 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:       <event-class>fault</event-class>
   data:       <reporting-entity>
   data:           <card>Ethernet0</card>
   data:       </reporting-entity>
   data:       <severity>major</severity>
   data:     </event>
   data: </notification>

   An example SSE event notification encoded using JSON:

   data: {
   data:   "ietf-restconf:notification": {
   data:     "event-time": "2013-12-21T00:01:00Z",
   data:     "example-mod:event": {
   data:       "event-class": "fault",
   data:       "reporting-entity": { "card": "Ethernet0" },
   data:       "severity": "major"
   data:     }
   data:   }
   data: }

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

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

      XML:

      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"><event-class>fault</event-class><re\
      portingEntity><card>Ethernet0</card></reporting-entity><severity>\
      major</severity></event></notification>



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      JSON:

      data: {"ietf-restconf:notification":{"event-time":"2013-12-21\
      T00:01:00Z","example-mod:event":{"event-class": "fault","repor\
      tingEntity":{"card":"Ethernet0"},"severity":"major"}}}

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

7.  Error Reporting

   HTTP status codes 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" and "5xx" class of status codes.

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

                 +-------------------------+-------------+
                 | error-tag               | status code |
                 +-------------------------+-------------+
                 | in-use                  | 409         |
                 | invalid-value           | 400 or 406  |
                 | (request) too-big       | 413         |
                 | (response) too-big      | 400         |
                 | missing-attribute       | 400         |
                 | bad-attribute           | 400         |
                 | unknown-attribute       | 400         |
                 | bad-element             | 400         |
                 | unknown-element         | 400         |
                 | unknown-namespace       | 400         |
                 | access-denied           | 403         |
                 | lock-denied             | 409         |



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                 | resource-denied         | 409         |
                 | rollback-failed         | 500         |
                 | data-exists             | 409         |
                 | data-missing            | 409         |
                 | operation-not-supported | 501         |
                 | operation-failed        | 412 or 500  |
                 | partial-operation       | 500         |
                 | malformed-message       | 400         |
                 +-------------------------+-------------+

                   Mapping from error-tag to status code

7.1.  Error Response Message

   When an error occurs for a request message on any resource type, and
   the status code that will be returned is in the "4xx" range (except
   for status code "403 Forbidden"), then the server SHOULD send a
   response message-body containing the information described by the
   "yang-errors" YANG template definition within the "ietf-restconf"
   module, found in Section 8.  The Content-Type of this response
   message MUST be a subtype of application/yang-data (see example
   below).

   The client SHOULD specify the desired encoding for error messages by
   specifying the appropriate media-type in the Accept header.  If no
   error media is specified, then the media subtype (e.g., XML or JSON)
   of the request message SHOULD be used, or the server MAY choose any
   supported message encoding format.  If there is no request message
   the server MUST select "application/yang-data" or "application/
   yang-data+json", depending on server preference.  All of the examples
   in this document, except for the one below, assume that XML encoding
   will be returned if there is an error.

   YANG Tree Diagram for <errors> data:

   +--ro errors
      +--ro error*
         +--ro error-type       enumeration
         +--ro error-tag        string
         +--ro error-app-tag?   string
         +--ro error-path?      instance-identifier
         +--ro error-message?   string
         +--ro error-info

   The semantics and syntax for RESTCONF error messages are defined with
   the "yang-errors" YANG data template extension, found in Section 8.

   Examples:



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   The following example shows an error returned for an "lock-denied"
   error that can occur if a NETCONF client has locked a datastore.  The
   RESTCONF client is attempting to delete a data resource.  Note that
   an Accept header is used to specify the desired encoding for the
   error message.  No response message-body content is expected by the
   client in this example.

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

   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-data+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 (some lines wrapped for display purposes):

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





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   <errors xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
     <error>
       <error-type>protocol</error-type>
       <error-tag>data-exists</error-tag>
       <error-path
         xmlns:rc="urn:ietf:params:xml:ns:yang:ietf-restconf"
         xmlns:jbox="https://example.com/ns/example-jukebox">
         /rc:restconf/rc:data/jbox:jukebox
       </error-path>
       <error-message>
         Data already exists, cannot create new resource
       </error-message>
     </error>
   </errors>

8.  RESTCONF module

   The "ietf-restconf" module defines conceptual definitions within an
   extension and two groupings, which are not meant to be implemented as
   datastore contents by a server.  E.g., the "restconf" container is
   not intended to be implemented as a top-level data node (under the "/
   restconf/data" entry point).

   Note that the "ietf-restconf" module does not have any protocol-
   accessible objects, so no YANG tree diagram is shown.

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

   <CODE BEGINS> file "ietf-restconf@2016-07-07.yang"

   module ietf-restconf {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-restconf";
     prefix "rc";

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

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

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

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



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

     description
       "This module contains conceptual YANG specifications
        for basic RESTCONF media type definitions used in
        RESTCONF protocol messages.

        Note that the YANG definitions within this module do not
        represent configuration data of any kind.
        The 'restconf-media-type' YANG extension statement
        provides a normative syntax for XML and JSON message
        encoding purposes.

        Copyright (c) 2016 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-15.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2016-07-07 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: RESTCONF Protocol.";
     }

     extension yang-data {
      argument name {
        yin-element true;
      }
      description
        "This extension is used to specify a YANG data template which



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         represents conceptual data defined in YANG. It is
         intended to describe hierarchical data independent of
         protocol context or specific message encoding format.
         Data definition statements within this extension specify
         the generic syntax for the specific YANG data template.

         Note that this extension does not define a media-type.
         A specification using this extension MUST specify the
         message encoding rules, including the content media type.

         The mandatory 'name' parameter value identifies the YANG
         data template that is being defined. It contains the
         template name.

         This extension is ignored unless it appears as a top-level
         statement. It SHOULD contain data definition statements
         that result in exactly one container data node definition.
         This allows compliant translation to an XML instance
         document for each YANG data template.

         The module name and namespace value for the YANG module using
         the extension statement is assigned to instance document data
         conforming to the data definition statements within
         this extension.

         The sub-statements of this extension MUST follow the
         'data-def-stmt' rule in the YANG ABNF.

         The XPath document root is the extension statement itself,
         such that the child nodes of the document root are
         represented by the data-def-stmt sub-statements within
         this extension. This conceptual document is the context
         for the following YANG statements:

            - must-stmt
            - when-stmt
            - path-stmt
            - min-elements-stmt
            - max-elements-stmt
            - mandatory-stmt
            - unique-stmt
            - ordered-by
            - instance-identifier data type

         The following data-def-stmt sub-statements have special
         meaning when used within a yang-data-resource extension
         statement.




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         - The list-stmt is not required to have a key-stmt defined.
         - The if-feature-stmt is ignored if present.
         - The config-stmt is ignored if present.
         - The available identity values for any 'identityref'
           leaf or leaf-list nodes is limited to the module
           containing this extension statement, and the modules
           imported into that module.
         ";
     }

     rc:yang-data yang-errors {
       uses errors;
     }

     rc:yang-data yang-api {
       uses restconf;
     }

     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 {
         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 {



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                 description "The server application layer";
               }
             }
             mandatory true;
             description
               "The protocol layer where the error occurred.";
           }

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

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

           leaf error-path {
             type instance-identifier;
             description
               "The YANG instance identifier associated
                with the error node.";
           }

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

           anydata error-info {
              description
                "This anydata value MUST represent a container with
                zero or more data nodes representing additional
                error information.";
           }
         }
       }
     }

     grouping restconf {
       description
         "Conceptual container representing the
          application/yang-api resource type.";



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       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
              state 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 the ietf-restconf-monitoring
              module.";
         }

         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.

              For example, the 'system-restart' RPC operation defined
              in the 'ietf-system' module would be represented as
              an empty leaf in the 'ietf-system' namespace. This is
              a conceptual leaf, and will not actually be found in
              the module:

                 module ietf-system {
                   leaf system-reset {
                     type empty;
                   }
                 }

              To invoke the 'system-restart' RPC operation:

                 POST /restconf/operations/ietf-system:system-restart

              To discover the RPC operations supported by the server:

                 GET /restconf/operations

              In XML the YANG module namespace identifies the module:

                <system-restart



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                   xmlns='urn:ietf:params:xml:ns:yang:ietf-system' />

              In JSON the YANG module name identifies the module:

                { 'ietf-system:system-restart' : [null] }

             ";
         }

         leaf yang-library-version {
           type string {
             pattern '\d{4}-\d{2}-\d{2}';
           }
           config false;
           mandatory true;
           description
             "Identifies the revision date of the ietf-yang-library
              module that is implemented by this RESTCONF server.
              Indicates the year, month, and day in YYYY-MM-DD
              numeric format.";
         }
       }
     }

   }

   <CODE ENDS>

9.  RESTCONF Monitoring

   The "ietf-restconf-monitoring" module provides information about the
   RESTCONF protocol capabilities and event notification streams
   available from the server.  A RESTCONF server MUST implement the "/
   restconf-state/capabilities" container in this module.

   YANG Tree Diagram for "ietf-restconf-monitoring" module:















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   +--ro restconf-state
      +--ro capabilities
      |  +--ro capability*   inet:uri
      +--ro streams
         +--ro stream* [name]
            +--ro name                        string
            +--ro description?                string
            +--ro replay-support?             boolean
            +--ro replay-log-creation-time?   yang:date-and-time
            +--ro access* [encoding]
               +--ro encoding  string
               +--ro location  inet:uri

9.1.  restconf-state/capabilities

   This mandatory container holds the RESTCONF protocol capability URIs
   supported by the server.

   The server MAY maintain a last-modified timestamp for this container,
   and return the "Last-Modified" header when this data node is
   retrieved with the GET or HEAD methods.  Note that the last-modified
   timestamp for the datastore resource is not affected by changes to
   this subtree.

   The server SHOULD maintain an entity-tag for this container, and
   return the "ETag" header when this data node is retrieved with the
   GET or HEAD methods.  Note that the entity-tag for the datastore
   resource is not affected by changes to this subtree.

   The server MUST include a "capability" URI leaf-list entry for the
   "defaults" mode used by the server, defined in Section 9.1.2.

   The server MUST include a "capability" URI leaf-list entry
   identifying each supported optional protocol feature.  This includes
   optional query parameters and MAY include other capability URIs
   defined outside this document.

9.1.1.  Query Parameter URIs

   A new set of RESTCONF Capability URIs are defined to identify the
   specific query parameters (defined in Section 4.8) supported by the
   server.

   The server MUST include a "capability" leaf-list entry for each
   optional query parameter that it supports.

   +-------------+-------+---------------------------------------------+
   | Name        | Secti | URI                                         |



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   |             | on    |                                             |
   +-------------+-------+---------------------------------------------+
   | depth       | 4.8.2 | urn:ietf:params:restconf:capability:depth:1 |
   |             |       | .0                                          |
   | fields      | 4.8.3 | urn:ietf:params:restconf:capability:fields: |
   |             |       | 1.0                                         |
   | filter      | 4.8.4 | urn:ietf:params:restconf:capability:filter: |
   |             |       | 1.0                                         |
   | replay      | 4.8.7 | urn:ietf:params:restconf:capability:replay: |
   |             | 4.8.8 | 1.0                                         |
   | with-       | 4.8.9 | urn:ietf:params:restconf:capability:with-   |
   | defaults    |       | defaults:1.0                                |
   +-------------+-------+---------------------------------------------+

                       RESTCONF Query Parameter URIs

9.1.2.  The "defaults" Protocol Capability URI

   This URI identifies the defaults handling mode that is used by the
   server for processing default leafs in requests for data resources.
   A parameter named "basic-mode" is required for this capability URI.
   The "basic-mode" definitions are specified in the "With-Defaults
   Capability for NETCONF" [RFC6243].

      +----------+--------------------------------------------------+
      | Name     | URI                                              |
      +----------+--------------------------------------------------+
      | defaults | urn:ietf:params:restconf:capability:defaults:1.0 |
      +----------+--------------------------------------------------+

                     RESTCONF defaults capability URI

   This protocol capability URI MUST be supported by the server, and
   MUST be listed in the "capability" leaf-list in Section 9.3.

   +------------------+------------------------------------------------+
   | Value            | Description                                    |
   +------------------+------------------------------------------------+
   | report-all       | No data nodes are considered default           |
   | trim             | Values set to the YANG default-stmt value are  |
   |                  | default                                        |
   | explicit         | Values set by the client are never considered  |
   |                  | default                                        |
   +------------------+------------------------------------------------+

   If the "basic-mode" is set to "report-all" then the server MUST
   adhere to the defaults handling behavior defined in Section 2.1 of
   [RFC6243].



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   If the "basic-mode" is set to "trim" then the server MUST adhere to
   the defaults handling behavior defined in Section 2.2 of [RFC6243].

   If the "basic-mode" is set to "explicit" then the server MUST adhere
   to the defaults handling behavior defined in Section 2.3 of
   [RFC6243].

   Example: (split for display purposes only)

   urn:ietf:params:restconf:capability:defaults:1.0?
        basic-mode=explicit

9.2.  restconf-state/streams

   This optional container provides access to the event notification
   streams supported by the server.  The server MAY omit this container
   if no event notification streams are supported.

   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 contains a URI that represents an event stream
   resource.

   Stream resources are defined in Section 3.8.  Notifications are
   defined in Section 6.

9.3.  RESTCONF Monitoring Module

   The "ietf-restconf-monitoring" module defines monitoring information
   for the RESTCONF protocol.

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

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

   <CODE BEGINS> file "ietf-restconf-monitoring@2016-07-07.yang"

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

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

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



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

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

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

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

     description
       "This module contains monitoring information for the
        RESTCONF protocol.

        Copyright (c) 2016 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-15.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2016-07-07 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: RESTCONF Protocol.";
     }

     container restconf-state {
       config false;
       description



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         "Contains RESTCONF protocol monitoring information.";

       container capabilities {
         description
           "Contains a list of protocol capability URIs";

         leaf-list capability {
           type inet:uri;
           description "A RESTCONF protocol capability URI.";
         }
       }

       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.
                If 'true', then the server MUST support the 'start-time'
                and 'stop-time' query parameters for this stream.";
             reference
               "RFC 5277, Section 3.4, <replaySupport> element.";
           }




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           leaf replay-log-creation-time {
             when "../replay-support" {
               description
                 "Only present if notification replay is supported";
             }
             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.";
           }

           list access {
             key encoding;
             min-elements 1;
             description
               "The server will create an entry in this list for each
                encoding format that is supported for this stream.
                The media type 'text/event-stream' is expected
                for all event streams. This list identifies the
                sub-types supported for this stream.";

             leaf encoding {
               type string;
               description
                 "This is the secondary encoding format within the
                  'text/event-stream' encoding used by all streams.
                  The type 'xml' is supported for XML encoding.
                  The type 'json' is supported for JSON encoding.";
             }

             leaf location {
               type inet:uri;
               mandatory true;
               description
                 "Contains a URL that represents the entry point
                  for establishing notification delivery via server
                  sent events.";
             }
           }
         }
       }
     }

   }




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   <CODE ENDS>

10.  YANG Module Library

   The "ietf-yang-library" module defined in
   [I-D.ietf-netconf-yang-library] provides information about the YANG
   modules and submodules used by the RESTCONF server.  Implementation
   is mandatory for RESTCONF servers.  All YANG modules and submodules
   used by the server MUST be identified in the YANG module library.

10.1.  modules-state

   This mandatory container holds the identifiers for the YANG data
   model modules supported by the server.

10.1.1.  modules-state/module

   This mandatory list contains one entry for each YANG data model
   module supported by the server.  There MUST be an instance of this
   list for every YANG module that is used by the server.

   The contents of this list are defined in the "module" YANG list
   statement in [I-D.ietf-netconf-yang-library].

11.  IANA Considerations

11.1.  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:  RFCXXXX

   `









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11.2.  YANG Module Registry

   This document registers two URIs as namespaces in the IETF XML
   registry [RFC3688].  Following the format in RFC 3688, the following
   registration is requested:

        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.

        URI: urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring
        Registrant Contact: The NETMOD WG of the IETF.
        XML: N/A, the requested URI is an XML namespace.

   This document registers two YANG modules 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:    RFCXXXX

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

11.3.  Media Types

11.3.1.  Media Type application/yang-data

      Type name: application

      Subtype name: yang-data

      Required parameters: None

      Optional parameters: None

     // RFC Ed.: replace draft-ietf-netmod-rfc6020bis with
     // the actual RFC reference for YANG 1.1, and remove this note.

      Encoding considerations: 8-bit
         Each conceptual YANG data node is encoded according to the
         XML Encoding Rules and Canonical Format for the specific
         YANG data node type defined in [draft-ietf-netmod-rfc6020bis].



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     // RFC Ed.: replace 'NN' in Section NN of [RFCXXXX] with the
     // section number for Security Considerations
     // Replace 'XXXX' in Section NN of [RFCXXXX] with the actual
     // RFC number, and remove this note.

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

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

      Interoperability considerations: [RFCXXXX] specifies the
         format of conforming messages and the interpretation
         thereof.

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

      Published specification: RFC XXXX

      Applications that use this media type: Instance document
        data parsers used within a protocol or automation tool
        that utilize YANG defined data structures.

      Fragment identifier considerations: The fragment field in the
         request URI has no defined purpose.

      Additional information:

        Deprecated alias names for this type: N/A
        Magic number(s): N/A
        File extension(s): .xml
        Macintosh file type code(s): "TEXT"

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

      Person & email address to contact for further information: See
         Authors' Addresses section of [RFCXXXX].

      Intended usage: COMMON

      Restrictions on usage: N/A



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

      Author: See Authors' Addresses section of [RFCXXXX].

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

      Provisional registration? (standards tree only): no

11.3.2.  Media Type application/yang-data+json

      Type name: application

      Subtype name: yang-data+json

      Required parameters: None

      Optional parameters: None

     // RFC Ed.: replace draft-ietf-netmod-yang-json with
     // the actual RFC reference for JSON Encoding of YANG Data,
     //  and remove this note.

     // RFC Ed.: replace draft-ietf-netmod-yang-metadata with
     // the actual RFC reference for JSON Encoding of YANG Data,
     //  and remove this note.

      Encoding considerations: 8-bit
         Each conceptual YANG data node is encoded according to
         [draft-ietf-netmod-yang-json]. A data annotation is
         encoded according to [draft-ietf-netmod-yang-metadata]

     // RFC Ed.: replace 'NN' in Section NN of [RFCXXXX] with the
     // section number for Security Considerations
     // Replace 'XXXX' in Section NN of [RFCXXXX] with the actual
     // RFC number, and remove this note.

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

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



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      Interoperability considerations: [RFCXXXX] specifies the format
         of conforming messages and the interpretation thereof.

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

      Published specification: RFC XXXX

      Applications that use this media type: Instance document
        data parsers used within a protocol or automation tool
        that utilize YANG defined data structures.

      Fragment identifier considerations: The syntax and semantics
         of fragment identifiers are the same as specified for the
        "application/json" media type.

      Additional information:

        Deprecated alias names for this type: N/A
        Magic number(s): N/A
        File extension(s): .json
        Macintosh file type code(s): "TEXT"

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

      Person & email address to contact for further information: See
         Authors' Addresses section of [RFCXXXX].

      Intended usage: COMMON

      Restrictions on usage: N/A

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

      Author: See Authors' Addresses section of [RFCXXXX].

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

      Provisional registration? (standards tree only): no









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11.4.  RESTCONF Capability URNs

   [Note to RFC Editor:
    The RESTCONF Protocol Capability Registry does not yet exist;
    Need to ask IANA to create it; remove this note for publication
   ]

   This document defines a registry for RESTCONF capability identifiers.
   The name of the registry is "RESTCONF Capability URNs".  The review
   policy for this registry is "IETF Review".  The registry shall record
   for each entry:

   o  the name of the RESTCONF capability.  By convention, this name
      begins with the colon ':' character.

   o  the URN for the RESTCONF capability.

   This document registers several capability identifiers in "RESTCONF
   Capability URNs" registry:

     Index
        Capability Identifier
     ------------------------

     :defaults
         urn:ietf:params:restconf:capability:defaults:1.0

     :depth
         urn:ietf:params:restconf:capability:depth:1.0

     :fields
         urn:ietf:params:restconf:capability:fields:1.0

     :filter
         urn:ietf:params:restconf:capability:filter:1.0

     :replay
         urn:ietf:params:restconf:capability:replay:1.0

     :with-defaults
         urn:ietf:params:restconf:capability:with-defaults:1.0

12.  Security Considerations

   The "ietf-restconf-monitoring" YANG module defined in this memo is
   designed to be accessed via the NETCONF protocol [RFC6241].  The
   lowest NETCONF layer is the secure transport layer, and the
   mandatory-to-implement secure transport is Secure Shell (SSH)



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   [RFC6242].  The NETCONF access control model [RFC6536] provides the
   means to restrict access for particular NETCONF users to a pre-
   configured subset of all available NETCONF protocol operations and
   content.

   This section provides security considerations for the resources
   defined by the RESTCONF protocol.  Security considerations for HTTPS
   are defined in [RFC7230].  RESTCONF does not specify which YANG
   modules a server needs to support.  Security considerations for the
   YANG-defined content manipulated by RESTCONF can be found in the
   documents defining those YANG modules.

   This document does not require use of a specific client
   authentication mechanism or authorization model, but it does require
   that a client authentication mechanism and authorization model is
   used whenever a client accesses a protected resource.  Client
   authentication MUST be implemented using client certificates or MUST
   be implemented using an HTTP authentication scheme.  Client
   authorization MAY be configured using the NETCONF Access Control
   Model (NACM) [RFC6536].

   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 a "401 Unauthorized"
   status-line.  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.  Note that it is possible
   for a client to detect configuration changes in data resources it is
   not authorized to access by monitoring changes in the ETag and Last-
   Modified header fields returned by the server for the datastore
   resource.

13.  Acknowledgements

   The authors would like to thank the following people for their
   contributions to this document: Ladislav Lhotka, Juergen
   Schoenwaelder, Rex Fernando, Robert Wilton, and Jonathan Hansford.





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   The authors would like to thank the following people for their
   excellent technical reviews of this document: Mehmet Ersue, Mahesh
   Jethanandani, Qin Wu, Joe Clarke, Bert Wijnen, Ladislav Lhotka,
   Rodney Cummings, Frank Xialiang, Tom Petch, Robert Sparks, Balint
   Uveges, Randy Presuhn, Sue Hares, Mark Nottingham, Benoit Claise, and
   Dale Worley.

   Contributions to this material by Andy Bierman are based upon work
   supported by the United States Army, Space & Terrestrial
   Communications Directorate (S&TCD) under Contract No.
   W15P7T-13-C-A616.  Any opinions, findings and conclusions or
   recommendations expressed in this material are those of the author(s)
   and do not necessarily reflect the views of The Space & Terrestrial
   Communications Directorate (S&TCD).

14.  References

14.1.  Normative References

   [I-D.ietf-netconf-yang-library]
              Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", draft-ietf-netconf-yang-library-06 (work in
              progress), April 2016.

   [I-D.ietf-netmod-rfc6020bis]
              Bjorklund, M., "The YANG 1.1 Data Modeling Language",
              draft-ietf-netmod-rfc6020bis-14 (work in progress), June
              2016.

   [I-D.ietf-netmod-yang-json]
              Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              draft-ietf-netmod-yang-json-10 (work in progress), March
              2016.

   [I-D.ietf-netmod-yang-metadata]
              Lhotka, L., "Defining and Using Metadata with YANG",
              draft-ietf-netmod-yang-metadata-07 (work in progress),
              March 2016.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              November 1996.

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

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



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

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [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.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, March 2011.

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

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <http://www.rfc-editor.org/info/rfc6242>.

   [RFC6243]  Bierman, A. and B. Lengyel, "With-defaults Capability for
              NETCONF", RFC 6243, 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.




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   [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.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <http://www.rfc-editor.org/info/rfc7159>.

   [RFC7230]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Message Syntax and Routing", RFC 7230, June
              2014.

   [RFC7231]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Semantics and Content", RFC 7231, June 2014.

   [RFC7232]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Conditional Requests", RFC 7232, June 2014.

   [RFC7235]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
              (HTTP/1.1): Authentication", RFC 7235, June 2014.

   [RFC7320]  Nottingham, M., "URI Design and Ownership", BCP 190, RFC
              7320, July 2014.

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI
              10.17487/RFC7540, May 2015,
              <http://www.rfc-editor.org/info/rfc7540>.

   [RFC7589]  Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
              NETCONF Protocol over Transport Layer Security (TLS) with
              Mutual X.509 Authentication", RFC 7589, DOI 10.17487/
              RFC7589, June 2015,
              <http://www.rfc-editor.org/info/rfc7589>.

   [W3C.REC-eventsource-20150203]
              Hickson, I., "Server-Sent Events", World Wide Web
              Consortium Recommendation REC-eventsource-20150203,
              February 2015,
              <http://www.w3.org/TR/2015/REC-eventsource-20150203>.

   [W3C.REC-html5-20141028]







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              Hickson, I., Berjon, R., Faulkner, S., Leithead, T.,
              Navara, E., O'Connor, E., and S. Pfeiffer, "HTML5", World
              Wide Web Consortium Recommendation REC-html5-20141028,
              October 2014,
              <http://www.w3.org/TR/2014/REC-html5-20141028>.

   [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>.

   [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>.

14.2.  Informative References

   [I-D.ietf-netconf-yang-patch]
              Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch
              Media Type", draft-ietf-netconf-yang-patch-08 (work in
              progress), March 2016.

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

Appendix A.  Change Log

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

   The RESTCONF issue tracker can be found here: https://github.com/
   netconf-wg/restconf/issues

A.1.  v14 to v15

   o  added text for HTTP/2 usage

   o  changed media type definitions per review comments

   o  added some clarifications and typos

   o  added error-tag mapping for 406 and 412 errors

A.2.  v13 - v14




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   This release addresses github issues #61, #62, #63, #65, #66, and
   #67.

   o  change term 'server' to 'NETCONF server'

   o  add term 'RESTCONF server' also called 'server'

   o  change term 'client' to 'NETCONF client'

   o  add term 'RESTCONF client' also called 'client'

   o  remove unused YANG terms

   o  clarified operation resource and schema resource terms

   o  clarified abstract and intro: RESTCONF uses NETCONF datastore
      concepts

   o  removed term 'protocol operation'; use 'RPC operation' instead

   o  clarified edit operation from NETCONF as nc:operation

   o  clarified retrieval of an operation resource

   o  remove ETag and Last-Modified requirements for /modules-state and
      /modules-state/module objects, since these are not configuration
      data nodes

   o  clarified Last-Modified and ETag requirements for datastore and
      data resources

   o  clarified defaults retrieval for leaf and leaf-list target
      resources

   o  clarified request message-body for operation resources

   o  clarified query parameters for GET also allowed for HEAD

   o  clarified error handling for query parameters

   o  clarified XPath function library for "filter" parameter

   o  added example for 'edit a data resource'

   o  added term 'notification replay' from RFC 5277

   o  clarified unsupported encoding format error handling




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   o  change term 'meta-data' to 'metadata'

   o  clarified RESTCONF metadata definition

   o  clarified error info not returned for 1xx, 2xx, and 3xx ranges

   o  clarified operations description in ietf-restconf module

   o  clarified Acknowledgements section

   o  clarified some examples

   o  update some references

   o  update RFC 2119 boilerplate

   o  remove requirements that simply restate HTTP requirements

   o  remove Pragma: no-cache from examples since RFC 7234 says this
      pragma is not defined for responses

   o  remove suggestion MAY send Pragma: no-cache in response

   o  remove table of HTTP status codes used in RESTCONF

   o  changed media type names so they conform to RFC 6838

   o  clarified too-big error-tag conversion

   o  update SSE reference

   o  clarify leaf-list identifier encoding

   o  removed all media types except yang-data

   o  changed restconf-media-type extension to be more generic yang-data
      extension

A.3.  v12 - v13

   o  fix YANG library module examples (now called module-state)

   o  fix terminology idnit issue

   o  removed RFC 2818 reference (changed citation to RFC 7230)

A.4.  v11 - v12




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   o  clarify query parameter requirements

   o  move filter query section to match table order in sec. 4.8

   o  clarify that depth default is entire subtree for datastore
      resource

   o  change ietf-restconf to YANG 1.1 to use anydata instead of anyxml

   o  made implementation of timestamps optional since ETags are
      mandatory

   o  removed confusing text about data resource definition revision
      date

   o  clarify that errors should be returned for any resource type

   o  clarified media subtype (not type) for error response

   o  clarified client SHOULD (not MAY) specify errors format in Accept
      header

   o  clarified terminology in many sections

A.5.  v10 - v11

   o  change term 'operational data' to 'state data'

   o  clarify :startup behavior

   o  clarify X.509 security text

   o  change '403 Forbidden' to '401 Unauthorized' for GET error

   o  clarify MUST have one "restconf" link relation

   o  clarify that NV-storage is not mandatory

   o  clarify how "Last-Modified" and "ETag" header info can be used by
      a client

   o  clarify meaning of mandatory parameter

   o  fix module name in action examples

   o  clarify operation resource request needs to be known to parse the
      output




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   o  clarify ordered-by user terminology

   o  fixed JSON example in D.1.1

A.6.  v09 - v10

   o  address review comments: github issue #36

   o  removed intro text about no knowledge of NETCONF needed

   o  clarified candidate and confirmed-commit behavior in sec. 1.3

   o  clarified that a RESTCONF server MUST support TLS

   o  clarified choice of 403 or 404 error

   o  fixed forward references to URI template (w/reference at first
      use)

   o  added reference to HTML5

   o  made error terminology more consistent

   o  clarified that only 1 list or leaf-list instance can be returned
      in an XML response message-body

   o  clarified that more than 1 instance must not be created by a POST
      method

   o  clarified that PUT cannot be used to change a leaf-list value or
      any list key values

   o  clarified that PATCH cannot be used to change a leaf-list value or
      any list key values

   o  clarified that DELETE should not be used to delete more than one
      instance of a leaf-list or list

   o  update JSON RFC reference

   o  specified that leaf-list instances are data resources

   o  specified how a leaf-list instance identifier is constructed

   o  fixed get-schema example






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   o  clarified that if no Accept header the server SHOULD return the
      type specified in RESTCONF, but MAY return any media-type,
      according to HTTP rules

   o  clarified that server SHOULD maintain timestamp and etag for data
      resources

   o  clarified default for content query parameter

   o  moved terminology section earlier in doc to avoid forward usage

   o  clarified intro text wrt/ interactions with NETCONF and access to
      specific datastores

   o  clarified server implementation requirements for YANG defaults

   o  clarified that Errors is not a resource, just a media type

   o  clarified that HTTP without TLS MUST NOT be used

   o  add RESTCONF Extensibility section to make it clear how RESTCONF
      will be extended in the future

   o  add text warning that NACM does not work with HTTP caching

   o  remove sec. 5.2 Message Headers

   o  remove 202 Accepted from list of used status-lines -- not allowed

   o  made implementation of OPTIONS MUST instead of SHOULD

   o  clarified that successful PUT for altering data returns 204

   o  fixed "point" parameter example

   o  added example of alternate value for root resource discovery

   o  added YANG action examples

   o  fixed some JSON examples

   o  changed default value for content query parameter to "all"

   o  changed empty container JSON encoding from "[null]" to "{}"

   o  added mandatory /restconf/yang-library-version leaf to advertise
      revision-date of the YANG library implemented by the server




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   o  clarified URI encoding rules for leaf-list

   o  clarified sec. 2.2 wrt/ certificates and TLS

   o  added update procedure for entity tag and timestamp

A.7.  v08 - v09

   o  fix introduction text regarding implementation requirements for
      the ietf-yang-library

   o  clarified HTTP authentication requirements

   o  fix host-meta example

   o  changed list key encoding to clarify that quoted strings are not
      allowed.  Percent-encoded values are used if quotes would be
      required.  A missing key is treated as a zero-length string

   o  Fixed example of percent-encoded string to match YANG model

   o  Changed streams examples to align with naming already used

A.8.  v07 - v08

   o  add support for YANG 1.1 action statement

   o  changed mandatory encoding from XML to XML or JSON

   o  fix syntax in fields parameter definition

   o  add meta-data encoding examples for XML and JSON

   o  remove RFC 2396 references and update with 3986

   o  change encoding of a key so quoted string are not used, since they
      are already percent-encoded.  A zero-length string is not encoded
      (/list=foo,,baz)

   o  Add example of percent-encoded key value

A.9.  v06 - v07

   o  fixed all issues identified in email from Jernej Tuljak in netconf
      email 2015-06-22

   o  fixed error example bug where error-urlpath was still used.
      Changed to error-path.



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   o  added mention of YANG Patch and informative reference

   o  added support for YANG 1.1, specifically support for anydata and
      actions

   o  removed the special field value "*", since it is no longer needed

A.10.  v05 - v06

   o  fixed RESTCONF issue #23 (ietf-restconf-monitoring bug)

A.11.  v04 - v05

   o  changed term 'notification event' to 'event notification'

   o  removed intro text about framework and meta-model

   o  removed early mention of API resources

   o  removed term unified datastore and cleaned up text about NETCONF
      datastores

   o  removed text about not immediate persistence of edits

   o  removed RESTCONF-specific data-resource-identifier typedef and its
      usage

   o  clarified encoding of key leafs

   o  changed several examples from JSON to XML encoding

   o  made 'insert' and 'point' query parameters mandatory to implement

   o  removed ":insert" capability URI

   o  renamed stream/encoding to stream/access

   o  renamed stream/encoding/type to stream/access/encoding

   o  renamed stream/encoding/events to stream/access/location

   o  changed XPath from informative to normative reference

   o  changed rest-dissertation from normative to informative reference

   o  changed example-jukebox playlist 'id' from a data-resource-
      identifier to a leafref pointing at the song name




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A.12.  v03 - v04

   o  renamed 'select' to 'fields' (#1)

   o  moved collection resource and page capability to draft-ietf-
      netconf-restconf-collection-00 (#3)

   o  added mandatory "defaults" protocol capability URI (#4)

   o  added optional "with-defaults" query parameter URI (#4)

   o  clarified authentication procedure (#9)

   o  moved ietf-yang-library module to draft-ietf-netconf-yang-
      library-00 (#13)

   o  clarified that JSON encoding of module name in a URI MUST follow
      the netmod-yang-json encoding rules (#14)

   o  added restconf-media-type extension (#15)

   o  remove "content" query parameter URI and made this parameter
      mandatory (#16)

   o  clarified datastore usage

   o  changed lock-denied error example

   o  added with-defaults query parameter example

   o  added term "RESTCONF Capability"

   o  changed NETCONF Capability URI registry usage to new RESTCONF
      Capability URI Registry usage

A.13.  v02 - v03

   o  added collection resource

   o  added "page" query parameter capability

   o  added "limit" and "offset" query parameters, which are available
      if the "page" capability is supported

   o  added "stream list" term

   o  fixed bugs in some examples




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   o  added "encoding" list within the "stream" list to allow different
      <events> URLs for XML and JSON encoding.

   o  made XML MUST implement and JSON MAY implement for servers

   o  re-add JSON notification examples (previously removed)

   o  updated JSON references

A.14.  v01 - v02

   o  moved query parameter definitions from the YANG module back to the
      plain text sections

   o  made all query parameters optional to implement

   o  defined query parameter capability URI

   o  moved 'streams' to new YANG module (ietf-restconf-monitoring)

   o  added 'capabilities' container to new YANG module (ietf-restconf-
      monitoring)

   o  moved 'modules' container to new YANG module (ietf-yang-library)

   o  added new leaf 'module-set-id' (ietf-yang-library)

   o  added new leaf 'conformance' (ietf-yang-library)

   o  changed 'schema' leaf to type inet:uri that returns the location
      of the YANG schema (instead of returning the schema directly)

   o  changed 'events' leaf to type inet:uri that returns the location
      of the event stream resource (instead of returning events
      directly)

   o  changed examples for yang.api resource since the monitoring
      information is no longer in this resource

   o  closed issue #1 'select parameter' since no objections to the
      proposed syntax

   o  closed "encoding of list keys" issue since no objection to new
      encoding of list keys in a target resource URI.

   o  moved open issues list to the issue tracker on github





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A.15.  v00 - v01

   o  fixed content=nonconfig example (non-config was incorrect)

   o  closed open issue 'message-id'.  There is no need for a message-id
      field, and RFC 2392 does not apply.

   o  closed open issue 'server support verification'.  The headers used
      by RESTCONF are widely supported.

   o  removed encoding rules from section on RESTCONF Meta-Data.  This
      is now defined in "I-D.lhotka-netmod-yang-json".

   o  added media type application/yang.errors to map to errors YANG
      grouping.  Updated error examples to use new media type.

   o  closed open issue 'additional datastores'.  Support may be added
      in the future to identify new datastores.

   o  closed open issue 'PATCH media type discovery'.  The section on
      PATCH has an added sentence on the Accept-Patch header.

   o  closed open issue 'YANG to resource mapping'.  Current mapping of
      all data nodes to resources will be used in order to allow
      mandatory DELETE support.  The PATCH operation is optional, as
      well as the YANG Patch media type.

   o  closed open issue '_self links for HATEOAS support'.  It was
      decided that they are redundant because they can be derived from
      the YANG module for the specific data.

   o  added explanatory text for the 'select' parameter.

   o  added RESTCONF Path Resolution section for discovering the root of
      the RESTCONF API using the /.well-known/host-meta.

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

   o  added Secure Transport section requiring TLS

   o  added Security Considerations section

   o  removed all references to "REST-like"

A.16.  bierman:restconf-04 to ietf:restconf-00

   o  updated open issues section




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Appendix B.  Open Issues

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

   The RESTCONF issues are tracked on github.com:

   https://github.com/netconf-wg/restconf/issues

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       leafref
      +--rw player
         +--rw gap?   decimal64

   rpcs:







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   +---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";

      organization "Example, Inc.";
      contact "support at example.com";
      description "Example Jukebox Data Model Module";
      revision "2015-04-04" {
        description "Initial version.";
        reference "example.com document 1-4673";
      }

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

      // abbreviated list of genre classifications
      identity alternative {
        base genre;
        description "Alternative music";
      }
      identity blues {
        base genre;
        description "Blues music";
      }
      identity country {
        base genre;
        description "Country music";
      }
      identity jazz {
        base genre;
        description "Jazz music";
      }
      identity pop {
        base genre;
        description "Pop music";
      }
      identity rock {
        base genre;
        description "Rock music";



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      }

      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.";



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              }

              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



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                     '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.";
          }



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          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 leafref {
                path "/jbox:jukebox/jbox:library/jbox:artist/" +
                     "jbox:album/jbox:song/jbox:name";
              }
              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";
          }



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          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 8 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 starts by retrieving the RESTCONF entry point:

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

   The server might respond:

   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>

   The client may then retrieve the top-level API resource, using the
   entry point "/restconf".

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

   The server might respond as follows:





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   [RFC Editor Note: Adjust the date (2016-04-09) for ietf-yang-library
   below to the date in the published ietf-yang-library YANG module, and
   remove this note.]

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

      {
        "ietf-restconf:restconf": {
          "data" : {},
          "operations" : {},
          "yang-library-version" : "2016-04-09"
        }
      }

   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-data

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

   [RFC Editor Note: Adjust the date for ietf-yang-library below to the
   date in the published ietf-yang-library YANG module, and remove this
   note.]

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

   <restconf xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
     <data/>
     <operations/>
     <yang-library-version>2016-04-09</yang-library-version>
   </restconf>









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D.1.2.  Retrieve The Server Module Information

   It is possible the YANG library module will change over time.  The
   client can retrieve the revision date of the ietf-yang-library
   supported by the server from the API resource, as described in the
   previous section.

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

   GET /restconf/data/ietf-yang-library:modules-state HTTP/1.1
   Host: example.com
   Accept: application/yang-data+json

   The server might respond as follows (some strings wrapped for display
   purposes):

   [RFC Editor Note: Adjust the date for ietf-yang-library below to the
   date in the published ietf-yang-library YANG module, and remove this
   note.]

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

      {
        "ietf-yang-library:modules-state": {
          "module-set-id": "5479120c17a619545ea6aff7aa19838b036ebbd7",
          "module": [
            {
              "name" : "foo",
              "revision" : "2012-01-02",
              "schema" : "https://example.com/modules/foo/2012-01-02",
              "namespace" : "http://example.com/ns/foo",
              "feature" : [ "feature1", "feature2" ],
              "deviation" : [
                {
                  "name" : "foo-dev",
                  "revision" "2012-02-16"
                }
              ],
              "conformance-type" : "implement"
            },
            {
              "name" : "ietf-yang-library",



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              "revision" : "2016-04-09",
              "schema" : "https://example.com/modules/ietf-yang-
                library/2016-04-09",
              "namespace" :
                "urn:ietf:params:xml:ns:yang:ietf-yang-library",
              "conformance-type" : "implement"
            },
            {
              "name" : "foo-types",
              "revision" : "2012-01-05",
              "schema" :
                "https://example.com/modules/foo-types/2012-01-05",
              "namespace" : "http://example.com/ns/foo-types",
              "conformance-type" : "import"
            },
            {
              "name" : "bar",
              "revision" : "2012-11-05",
              "schema" : "https://example.com/modules/bar/2012-11-05",
              "namespace" : "http://example.com/ns/bar",
              "feature" : [ "bar-ext" ],
              "conformance-type" : "implement",
              "submodule" : [
                {
                  "name" : "bar-submod1",
                  "revision" : "2012-11-05",
                  "schema" :
                   "https://example.com/modules/bar-submod1/2012-11-05"
                },
                {
                  "name" : "bar-submod2",
                  "revision" : "2012-11-05",
                  "schema" :
                   "https://example.com/modules/bar-submod2/2012-11-05"
                }
              ]
            }
          ]
        }
      }

D.1.3.  Retrieve The Server Capability Information

   In this example the client is retrieving the capability information
   from the server in XML format, and the server supports all the
   RESTCONF query parameters, plus one vendor parameter:





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   GET /restconf/data/ietf-restconf-monitoring:restconf-state/
       capabilities  HTTP/1.1
   Host: example.com
   Accept: application/yang-data

   The server might respond as follows.  The extra whitespace in
   'capability' elements is for display purposes only.

   HTTP/1.1 200 OK
   Date: Mon, 23 Apr 2012 17:02:00 GMT
   Server: example-server
   Cache-Control: no-cache
   Last-Modified: Sun, 22 Apr 2012 01:00:14 GMT
   Content-Type: application/yang-data

   <capabilities
       xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf-monitoring">
    <capability>
     urn:ietf:params:restconf:capability:defaults:1.0?
        basic-mode=explicit
    </capability>
    <capability>
     urn:ietf:params:restconf:capability:with-defaults:1.0
    </capability>
    <capability>
     urn:ietf:params:restconf:capability:depth:1.0
    </capability>
    <capability>
     urn:ietf:params:restconf:capability:fields:1.0
    </capability>
    <capability>
     urn:ietf:params:restconf:capability:filter:1.0
    </capability>
    <capability>
     urn:ietf:params:restconf:capability:start-time:1.0
    </capability>
    <capability>
     urn:ietf:params:restconf:capability:stop-time:1.0
    </capability>
    <capability>
     http://example.com/capabilities/myparam
    </capability>
   </capabilities>

D.2.  Edit Resource Examples

D.2.1.  Create New Data Resources




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   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: https://example.com/restconf/data/
       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  HTTP/1.1
   Host: example.com
   Content-Type: application/yang-data

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

   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: https://example.com/restconf/data/
       example-jukebox:jukebox/library/artist=Foo%20Fighters/



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       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 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 "genre" field is being updated.

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

      { "example-jukebox:genre" : "example-jukebox:alternative" }

   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.2.3.  Edit a Datastore Resource

   In this example, the client modifies two different data nodes by
   sending a PATCH to the datastore resource:

   PATCH /restconf/data HTTP/1.1
   Host: example.com
   Content-Type: application/yang-data

   <data xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
     <jukebox xmlns="http://example.com/ns/example-jukebox">
       <library>
         <artist>
           <name>Foo Fighters</name>
           <album>
             <name>Wasting Light</name>
             <year>2011</year>



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           </album>
         </artist>
         <artist>
           <name>Nick Cave and the Bad Seeds</name>
           <album>
             <name>Tender Prey</name>
             <year>1988</year>
           </album>
         </artist>
       </library>
     </jukebox>
   </data>

D.2.4.  Edit a Data Resource

   In this example, the client modifies one data nodes by sending a
   PATCH to the data resource (URI wrapped for display purposes only):

   PATCH /restconf/data/example-jukebox:jukebox/library/
      artist=Nick%20Cave%20and%20the%Bad%20Seeds HTTP/1.1
   Host: example.com
   Content-Type: application/yang-data

   <artist xmlns="http://example.com/ns/example-jukebox">
     <name>Nick Cave and the Bad Seeds</name>
     <album>
       <name>The Good Son</name>
       <year>1990</year>
     </album>
   </artist>

D.3.  Query Parameter Examples

D.3.1.  "content" Parameter

   The "content" parameter is used to select the type of data 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 child resources.

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



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         type uint32;
         config false;
       }
     }
   }

   Example 1: content=all

   To retrieve all the child resources, the "content" parameter is set
   to "all", or omitted, since this is the default value.  The client
   might send:

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

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:11:30 GMT
      Server: example-server
      Cache-Control: 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 child resources, the "content"
   parameter is set to "config".  Note that the "ETag" and
   "Last-Modified" headers are only returned if the content parameter
   value is "config".



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

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:11:30 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
      ETag: "eeeada438af"
      Cache-Control: 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=nonconfig

   To retrieve only the non-configuration child resources, the "content"
   parameter is set to "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=nonconfig
       HTTP/1.1
   Host: example.com
   Accept: application/yang-data+json

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:11:30 GMT
      Server: example-server
      Cache-Control: no-cache



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      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 child
   resources that are returned by the server for a GET method request.

   The depth parameter starts counting levels at the level of the target
   resource that is specified, so that a depth level of "1" includes
   just the target resource level itself.  A depth level of "2" includes
   the target resource level and its child nodes.

   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 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

   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



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      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" : "https://example.com/restconf/data/
                        example-jukebox:jukebox/library/artist=
                        Foo%20Fighters/album=Wasting%20Light/
                        song=Rope"
                },
                {
                  "index" : 2,
                  "id" : "https://example.com/restconf/data/



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                        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

   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
      Content-Type: application/yang-data+json

      {
        "example-jukebox:jukebox" : {}
      }

   Example 3: depth=3

   To limit the depth level to the target resource plus 2 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

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:11:30 GMT
      Server: example-server



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      Cache-Control: no-cache
      Content-Type: application/yang-data+json

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

D.3.3.  "fields" Parameter

   In this example the client is retrieving the datastore resource in
   JSON format, but retrieving only the "modules-state/module" list, and
   only the "name" and "revision" nodes from each list entry.  Note that
   top node returned by the server matches the target resource node
   (which is "data" in this example).  The "module-set-id" leaf is not
   returned because it is not selected in the fields expression.

   GET /restconf/data?fields=ietf-yang-library:modules-state/
       module(name;revision) HTTP/1.1
   Host: example.com
   Accept: application/yang-data+json

   The server might respond as follows.

   [RFC Editor Note: Adjust the date for ietf-yang-library below to the
   date in the published ietf-yang-library YANG module, and remove this
   note.]

   [RFC Editor Note: Adjust the date for ietf-restconf-monitoring below
   to the date in the published ietf-restconf-monitoring YANG module,
   and remove this note.]

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2012 17:01:00 GMT
      Server: example-server



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      Content-Type: application/yang-data+json

      {
        "ietf-restconf:data" : {
          "ietf-yang-library:modules-state": {
            "module": [
              {
                "name" : "example-jukebox",
                "revision" : "2015-06-04"
              },
              {
                "name" : "ietf-inet-types",
                "revision" : "2013-07-15"
              },
              {
                "name" : "ietf-restconf-monitoring",
                "revision" : "2016-03-16"
              },
              {
                "name" : "ietf-yang-library",
                "revision" : "2016-04-09"
              },
              {
                "name" : "ietf-yang-types",
                "revision" : "2013-07-15"
              }
            ]
          }
        }
      }

D.3.4.  "insert" Parameter

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

   Request from client:

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

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



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         }
      }

   Response from server.  Note that the "Location" header line is
   wrapped for display purposes only:

   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: https://example.com/restconf/data/
       example-jukebox:jukebox/playlist=Foo-One/song=1
   ETag: "eeeada438af"

D.3.5.  "point" Parameter

   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%3DFoo%20Fighters%2Falbum%3D
          Wasting%20Light%2Fsong%3DBridge%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"





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D.3.6.  "filter" Parameter

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

      // filter = /event/event-class='fault'
      GET /streams/NETCONF?filter=%2Fevent%2Fevent-class%3D'fault'

      // filter = /event/severity<=4
      GET /streams/NETCONF?filter=%2Fevent%2Fseverity%3C%3D4

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

      // filter = /*/reporting-entity/card!='Ethernet0'
      GET /streams/NETCONF?
         filter=%2F*%2Freporting-entity%2Fcard%21%3D'Ethernet0'

      // filter = /*/email-addr[contains(.,'company.com')]
      GET /streams/critical-syslog?
         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 /streams/NETCONF?
        filter=(%2Fexample-mod%3Aevent1%2Fname%3D'joe'%20and
                %20%2Fexample-mod%3Aevent1%2Fstatus%3D'online')

      // To get notifications from just two modules (e.g., m1 + m2)
      // filter=(/m1:* or /m2:*)
      GET /streams/NETCONF?filter=(%2Fm1%3A*%20or%20%2Fm2%3A*)

D.3.7.  "start-time" Parameter

   // start-time = 2014-10-25T10:02:00Z
   GET /streams/NETCONF?start-time=2014-10-25T10%3A02%3A00Z

D.3.8.  "stop-time" Parameter

   // stop-time = 2014-10-25T12:31:00Z
   GET /mystreams/NETCONF?stop-time=2014-10-25T12%3A31%3A00Z









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D.3.9.  "with-defaults" Parameter

   The following YANG module is assumed for this example.

     module example-interface {
       prefix "exif";
       namespace "urn:example.com:params:xml:ns:yang:example-interface";

       container interfaces {
         list interface {
           key name;
           leaf name { type string; }
           leaf mtu { type uint32; }
           leaf status {
             config false;
             type enumeration {
               enum up;
               enum down;
               enum testing;
             }
           }
         }
       }
     }

   Assume the same data model as defined in Appendix A.1 of [RFC6243].
   Assume the same data set as defined in Appendix A.2 of [RFC6243].  If
   the server defaults-uri basic-mode is "trim", the the following
   request for interface "eth1" might be as follows:

   Without query parameter:

   GET /restconf/data/example:interfaces/interface=eth1 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:interface": [
          {
            "name" : "eth1",
            "status" : "up"



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          }
        ]
      }

   Note that the "mtu" leaf is missing because it is set to the default
   "1500", and the server defaults handling basic-mode is "trim".

   With query parameter:

   GET /restconf/data/example:interfaces/interface=eth1
       ?with-defaults=report-all 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:interface": [
          {
            "name" : "eth1",
            "mtu" : 1500,
            "status" : "up"
          }
        ]
      }

   Note that the server returns the "mtu" leaf because the "report-all"
   mode was requested with the "with-defaults" query parameter.

Authors' Addresses

   Andy Bierman
   YumaWorks

   Email: andy@yumaworks.com


   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com





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   Kent Watsen
   Juniper Networks

   Email: kwatsen@juniper.net















































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