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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: April 30, 2017                                   Tail-f Systems
                                                               K. Watsen
                                                        Juniper Networks
                                                        October 27, 2016


                           RESTCONF Protocol
                     draft-ietf-netconf-restconf-18

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 April 30, 2017.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of




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   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 . . . . . . . . . . . . . . . . . . . . . . . .   8
       1.1.6.  URI Template and Examples . . . . . . . . . . . . . .  10
       1.1.7.  Tree Diagrams . . . . . . . . . . . . . . . . . . . .  10
     1.2.  Subset of NETCONF Functionality . . . . . . . . . . . . .  11
     1.3.  Data Model Driven API . . . . . . . . . . . . . . . . . .  11
     1.4.  Coexistence with NETCONF  . . . . . . . . . . . . . . . .  12
     1.5.  RESTCONF Extensibility  . . . . . . . . . . . . . . . . .  13
   2.  Transport Protocol  . . . . . . . . . . . . . . . . . . . . .  15
     2.1.  Integrity and Confidentiality . . . . . . . . . . . . . .  15
     2.2.  HTTPS with X.509v3 Certificates . . . . . . . . . . . . .  15
     2.3.  Certificate Validation  . . . . . . . . . . . . . . . . .  15
     2.4.  Authenticated Server Identity . . . . . . . . . . . . . .  15
     2.5.  Authenticated Client Identity . . . . . . . . . . . . . .  16
   3.  Resources . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     3.1.  Root Resource Discovery . . . . . . . . . . . . . . . . .  17
     3.2.  RESTCONF Media Types  . . . . . . . . . . . . . . . . . .  19
     3.3.  API Resource  . . . . . . . . . . . . . . . . . . . . . .  19
       3.3.1.  {+restconf}/data  . . . . . . . . . . . . . . . . . .  20
       3.3.2.  {+restconf}/operations  . . . . . . . . . . . . . . .  20
       3.3.3.  {+restconf}/yang-library-version  . . . . . . . . . .  21
     3.4.  Datastore Resource  . . . . . . . . . . . . . . . . . . .  21
       3.4.1.  Edit Collision Prevention . . . . . . . . . . . . . .  22
     3.5.  Data Resource . . . . . . . . . . . . . . . . . . . . . .  23
       3.5.1.  Timestamp . . . . . . . . . . . . . . . . . . . . . .  24
       3.5.2.  Entity-Tag  . . . . . . . . . . . . . . . . . . . . .  24
       3.5.3.  Encoding Data Resource Identifiers in the Request URI  24
       3.5.4.  Default Handling  . . . . . . . . . . . . . . . . . .  28
     3.6.  Operation Resource  . . . . . . . . . . . . . . . . . . .  28
       3.6.1.  Encoding Operation Resource Input Parameters  . . . .  29
       3.6.2.  Encoding Operation Resource Output Parameters . . . .  34
       3.6.3.  Encoding Operation Resource Errors  . . . . . . . . .  36
     3.7.  Schema Resource . . . . . . . . . . . . . . . . . . . . .  37
     3.8.  Event Stream Resource . . . . . . . . . . . . . . . . . .  38
     3.9.  Errors YANG Data Template . . . . . . . . . . . . . . . .  39
   4.  RESTCONF Methods  . . . . . . . . . . . . . . . . . . . . . .  39
     4.1.  OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . .  40
     4.2.  HEAD  . . . . . . . . . . . . . . . . . . . . . . . . . .  40



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     4.3.  GET . . . . . . . . . . . . . . . . . . . . . . . . . . .  40
     4.4.  POST  . . . . . . . . . . . . . . . . . . . . . . . . . .  42
       4.4.1.  Create Resource Mode  . . . . . . . . . . . . . . . .  42
       4.4.2.  Invoke Operation Mode . . . . . . . . . . . . . . . .  44
     4.5.  PUT . . . . . . . . . . . . . . . . . . . . . . . . . . .  44
     4.6.  PATCH . . . . . . . . . . . . . . . . . . . . . . . . . .  46
       4.6.1.  Plain Patch . . . . . . . . . . . . . . . . . . . . .  47
     4.7.  DELETE  . . . . . . . . . . . . . . . . . . . . . . . . .  48
     4.8.  Query Parameters  . . . . . . . . . . . . . . . . . . . .  49
       4.8.1.  The "content" Query Parameter . . . . . . . . . . . .  50
       4.8.2.  The "depth" Query Parameter . . . . . . . . . . . . .  51
       4.8.3.  The "fields" Query Parameter  . . . . . . . . . . . .  51
       4.8.4.  The "filter" Query Parameter  . . . . . . . . . . . .  52
       4.8.5.  The "insert" Query Parameter  . . . . . . . . . . . .  53
       4.8.6.  The "point" Query Parameter . . . . . . . . . . . . .  54
       4.8.7.  The "start-time" Query Parameter  . . . . . . . . . .  54
       4.8.8.  The "stop-time" Query Parameter . . . . . . . . . . .  55
       4.8.9.  The "with-defaults" Query Parameter . . . . . . . . .  55
   5.  Messages  . . . . . . . . . . . . . . . . . . . . . . . . . .  57
     5.1.  Request URI Structure . . . . . . . . . . . . . . . . . .  57
     5.2.  Message Encoding  . . . . . . . . . . . . . . . . . . . .  58
     5.3.  RESTCONF Metadata . . . . . . . . . . . . . . . . . . . .  59
       5.3.1.  XML Metadata Encoding Example . . . . . . . . . . . .  60
       5.3.2.  JSON Metadata Encoding Example  . . . . . . . . . . .  60
     5.4.  Return Status . . . . . . . . . . . . . . . . . . . . . .  61
     5.5.  Message Caching . . . . . . . . . . . . . . . . . . . . .  61
   6.  Notifications . . . . . . . . . . . . . . . . . . . . . . . .  62
     6.1.  Server Support  . . . . . . . . . . . . . . . . . . . . .  62
     6.2.  Event Streams . . . . . . . . . . . . . . . . . . . . . .  62
     6.3.  Subscribing to Receive Notifications  . . . . . . . . . .  64
       6.3.1.  NETCONF Event Stream  . . . . . . . . . . . . . . . .  65
     6.4.  Receiving Event Notifications . . . . . . . . . . . . . .  65
   7.  Error Reporting . . . . . . . . . . . . . . . . . . . . . . .  67
     7.1.  Error Response Message  . . . . . . . . . . . . . . . . .  68
   8.  RESTCONF Module . . . . . . . . . . . . . . . . . . . . . . .  70
   9.  RESTCONF Monitoring . . . . . . . . . . . . . . . . . . . . .  77
     9.1.  restconf-state/capabilities . . . . . . . . . . . . . . .  77
       9.1.1.  Query Parameter URIs  . . . . . . . . . . . . . . . .  78
       9.1.2.  The "defaults" Protocol Capability URI  . . . . . . .  78
     9.2.  restconf-state/streams  . . . . . . . . . . . . . . . . .  79
     9.3.  RESTCONF Monitoring Module  . . . . . . . . . . . . . . .  79
   10. YANG Module Library . . . . . . . . . . . . . . . . . . . . .  83
     10.1.  modules-state/module . . . . . . . . . . . . . . . . . .  83
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  83
     11.1.  The "restconf" Relation Type . . . . . . . . . . . . . .  84
     11.2.  YANG Module Registry . . . . . . . . . . . . . . . . . .  84
     11.3.  Media Types  . . . . . . . . . . . . . . . . . . . . . .  85
       11.3.1.  Media Type application/yang-data+xml . . . . . . . .  85



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       11.3.2.  Media Type application/yang-data+json  . . . . . . .  86
     11.4.  RESTCONF Capability URNs . . . . . . . . . . . . . . . .  88
     11.5.  Registration of "restconf" URN sub-namespace . . . . . .  89
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  89
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  90
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  91
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  91
     14.2.  Informative References . . . . . . . . . . . . . . . . .  94
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  94
     A.1.  v17 to v18  . . . . . . . . . . . . . . . . . . . . . . .  94
     A.2.  v16 to v17  . . . . . . . . . . . . . . . . . . . . . . .  94
     A.3.  v15 to v16  . . . . . . . . . . . . . . . . . . . . . . .  95
     A.4.  v14 to v15  . . . . . . . . . . . . . . . . . . . . . . .  95
     A.5.  v13 - v14 . . . . . . . . . . . . . . . . . . . . . . . .  96
     A.6.  v12 - v13 . . . . . . . . . . . . . . . . . . . . . . . .  98
     A.7.  v11 - v12 . . . . . . . . . . . . . . . . . . . . . . . .  98
     A.8.  v10 - v11 . . . . . . . . . . . . . . . . . . . . . . . .  98
     A.9.  v09 - v10 . . . . . . . . . . . . . . . . . . . . . . . .  99
     A.10. v08 - v09 . . . . . . . . . . . . . . . . . . . . . . . . 101
     A.11. v07 - v08 . . . . . . . . . . . . . . . . . . . . . . . . 101
     A.12. v06 - v07 . . . . . . . . . . . . . . . . . . . . . . . . 102
     A.13. v05 - v06 . . . . . . . . . . . . . . . . . . . . . . . . 102
     A.14. v04 - v05 . . . . . . . . . . . . . . . . . . . . . . . . 102
     A.15. v03 - v04 . . . . . . . . . . . . . . . . . . . . . . . . 103
     A.16. v02 - v03 . . . . . . . . . . . . . . . . . . . . . . . . 103
     A.17. v01 - v02 . . . . . . . . . . . . . . . . . . . . . . . . 104
     A.18. v00 - v01 . . . . . . . . . . . . . . . . . . . . . . . . 105
     A.19. bierman:restconf-04 to ietf:restconf-00 . . . . . . . . . 106
   Appendix B.  Open Issues  . . . . . . . . . . . . . . . . . . . . 106
   Appendix C.  Example YANG Module  . . . . . . . . . . . . . . . . 106
     C.1.  example-jukebox YANG Module . . . . . . . . . . . . . . . 107
   Appendix D.  RESTCONF Message Examples  . . . . . . . . . . . . . 112
     D.1.  Resource Retrieval Examples . . . . . . . . . . . . . . . 112
       D.1.1.  Retrieve the Top-level API Resource . . . . . . . . . 112
       D.1.2.  Retrieve The Server Module Information  . . . . . . . 113
       D.1.3.  Retrieve The Server Capability Information  . . . . . 115
     D.2.  Edit Resource Examples  . . . . . . . . . . . . . . . . . 116
       D.2.1.  Create New Data Resources . . . . . . . . . . . . . . 116
       D.2.2.  Detect Resource Entity-Tag Change . . . . . . . . . . 117
       D.2.3.  Edit a Datastore Resource . . . . . . . . . . . . . . 118
       D.2.4.  Replace a Datastore Resource  . . . . . . . . . . . . 119
       D.2.5.  Edit a Data Resource  . . . . . . . . . . . . . . . . 120
     D.3.  Query Parameter Examples  . . . . . . . . . . . . . . . . 120
       D.3.1.  "content" Parameter . . . . . . . . . . . . . . . . . 120
       D.3.2.  "depth" Parameter . . . . . . . . . . . . . . . . . . 124
       D.3.3.  "fields" Parameter  . . . . . . . . . . . . . . . . . 127
       D.3.4.  "insert" Parameter  . . . . . . . . . . . . . . . . . 128
       D.3.5.  "point" Parameter . . . . . . . . . . . . . . . . . . 129



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       D.3.6.  "filter" Parameter  . . . . . . . . . . . . . . . . . 130
       D.3.7.  "start-time" Parameter  . . . . . . . . . . . . . . . 131
       D.3.8.  "stop-time" Parameter . . . . . . . . . . . . . . . . 131
       D.3.9.  "with-defaults" Parameter . . . . . . . . . . . . . . 132
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 133

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 [RFC7950], 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.  NETCONF also defines a protocol for invoking these
   operations.  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 with the NETCONF protocol, which are
   described in Section 1.4.  The RESTCONF server MAY provide access to
   specific datastores using operation resources, as described in
   Section 3.6.  The RESTCONF protocol does not specify any mandatory
   operation resources.  The semantics of each operation resource
   determine if and how datastores are accessed.

   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 field

   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 [RFC7950]:

   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






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1.1.5.  Terms

   The following terms are used within this document:

   o  API resource: the resource that models the RESTCONF root resource
      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  client: a RESTCONF client

   o  data resource: a resource that models a YANG data node.  It is
      defined with YANG data definition statements.

   o  datastore resource: the resource that models a programmatic
      interface using NETCONF datastore concepts.  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.  Event stream
      contents are described in Section 3.8.

   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, header fields, 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 PATCH method 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 media type for use with the PATCH method,
      defined in Section 4.6.1, that can be used for simple merge
      operations.  It is specified by a request Content-Type of
      "application/yang-data+xml" or "application/yang-data+json".

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

   o  resource type: one of the RESTCONF resource classes defined in
      this document.  One of "api", "datastore", "data", "operation",
      "schema", or "event stream".

   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 defined in Section 9.3.

   o  RESTCONF client: a client which implements the RESTCONF protocol.

   o  RESTCONF server: a server which implements the RESTCONF protocol.

   o  retrieval request: a request using the GET or HEAD methods.

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

   o  server: a RESTCONF server

   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.

   o  stream resource: An event stream resource.





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

   o  yang-data extension: A YANG external statement that conforms to
      the "yang-data" extension statement found in Section 8.  The yang-
      data extension is used to define YANG data structures that are
      meant to be used as YANG data templates.  These data structures
      are not intended to be implemented as part of a configuration
      datastore or as operational state within the server, so normal
      YANG data definition statements cannot be used.

   o  YANG data template: a schema for modeling protocol message
      components as conceptual data structure using YANG.  This allows
      the messages to be defined in an encoding-independent manner.
      Each YANG data template is defined with the "yang-data" extension,
      found in Section 8.  Representations of instances conforming to a
      particular YANG data template can be defined for YANG.  The XML
      representation is defined in YANG version 1.1 [RFC7950], and
      supported with the "application/yang-data+xml" media type.  The
      JSON representation is defined in JSON Encoding of Data Modeled
      with YANG [RFC7951], and supported with the "application/
      yang-data+json" media type.

1.1.6.  URI Template and Examples

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

   For simplicity, all of the examples in this document use "/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.

   Many protocol header lines and message-body text within examples
   throughout the document are split into multiple lines for display
   purposes only.  When a line ends with backslash ('\') as the last
   character, the line is wrapped for display purposes.  It is to be
   considered to be joined to the next line by deleting the backslash,
   the following line break, and the leading whitespace of the next
   line.

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:




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

   o  Abbreviations before data node names: "rw" means configuration
      data (read-write), "ro" state data (read-only), and "x" operation
      resource (executable)

   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.

   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 by a
   RESTCONF client.

   RESTCONF is not intended to replace NETCONF, but rather provide an
   HTTP interface that follows Representational State Transfer (REST)
   principles [rest-dissertation], and is compatible with the NETCONF
   datastore model.

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.
   Knowing the YANG modules used by the server, a client can derive all
   management resource URLs and the proper structure of all RESTCONF
   requests and responses.  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 utilizes the YANG Library [RFC7895] to allow a client to
   discover the YANG module conformance information for the server, in
   case the client wants to use it.

   The server can optionally support retrieval of the YANG modules it
   uses, as identified in its YANG library.  See Section 3.7 for
   details.

   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
   [RFC7895].  The server MUST implement the "ietf-yang-library" module,
   which MUST identify all the YANG modules used by the server, in the
   "modules-state/module" list.  The conceptual datastore contents,
   data-model-specific RPC 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.  Non-configuration data
   is also called "state data".

   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 data resource within the datastore resource is
   activated upon successful completion of the edit.

1.4.  Coexistence with NETCONF

   RESTCONF can be implemented on a device that supports the NETCONF
   protocol.

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

         +-----------+           +-----------------+
         |  Web app  | <-------> |                 |
         +-----------+  RESTCONF | network device  |
                                 |                 |
         +-----------+           |   +-----------+ |
         | NETCONF   | <-------> |   | datastore | |
         | Client    |  NETCONF  |   |           | |
         +-----------+           |   +-----------+ |
                                 +-----------------+




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   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  | <-------> |                 |
         +-----------+  RESTCONF | network device  |
                                 |                 |
                                 +-----------------+

   There are interactions between the NETCONF protocol and RESTCONF
   protocol related to edit operations.  It is possible that locks are
   in use on a RESTCONF server, even though RESTCONF cannot manipulate
   locks.  In such a case, the RESTCONF protocol will not be granted
   write access to data resources within a datastore.

   If the NETCONF server 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 by any NETCONF client, then any new commit will act as
   the confirming commit.  If the NETCONF 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.  There error-tag "in-use" is returned in this case.  The
   error-tag value "resource-denied" is used in this case.

   If the NETCONF server supports :startup, the RESTCONF server MUST
   automatically update the non-volatile startup configuration
   datastore, after the running datastore has been altered as a
   consequence of a RESTCONF edit operation.

   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.  There error-tag "in-use" is
   returned in this case.

1.5.  RESTCONF Extensibility

   There are two extensibility mechanisms built into RESTCONF:

   o  protocol version



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   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 RESTCONF root resource will be used which
   will be located using a different link relation (See Section 3.1).

   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.

   The client might send:

      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'/>
          <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.
   Currently this extension mechanism is used to identify optional query
   parameters that are supported, 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.




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2.  Transport Protocol

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], and SHOULD adhere to [RFC7525].  The
   RESTCONF protocol MUST NOT be used over HTTP without using the TLS
   protocol.

   RESTCONF does not require a specific version of HTTP.  However, it is
   RECOMMENDED that at least HTTP/1.1 [RFC7230] be supported by all
   implementations.

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 of
   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 server's TLS certificate with a certificate
   obtained by a trusted mechanism (e.g., a pinned certificate).  If
   X.509 certificate path validation fails, and the presented X.509
   certificate does not match a certificate obtained by a trusted
   mechanism, the connection MUST be terminated, as described in
   Section 7.2.1 of [RFC5246].

2.4.  Authenticated Server Identity

   The RESTCONF client MUST check the identity of the server according
   to Section 3.1 of [RFC2818].








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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].  The error-tag value
   "access-denied" is used in this case.

   To authenticate a client, a RESTCONF server SHOULD require TLS client
   certificate based authentication (Section 7.4.6 of [RFC5246]).  If
   certificate based authentication is not feasible (e.g., because one
   cannot build the required PKI for clients) then an HTTP
   authentication MAY be used.  In the latter case, one of the HTTP
   authentication schemes defined in the HTTP Authentication Scheme
   Registry (Section 5.1 in [RFC7235]) MUST be used.

   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 as 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 field in the
   HTTP response message.  A resource has one or more representations,
   each associated with a different media type.  When a representation
   of a resource is sent in an HTTP message, the associated media type
   is given in the "Content-Type" header.  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.



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   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 an RPC 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:

   The client might send:

      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>

   After discovering the RESTCONF API root, the client MUST use this
   value as the initial part of the path in the request URI, in any
   subsequent request for a RESTCONF resource.

   In this example, the client would use the path "/restconf" as the
   RESTCONF root resource.

   Example returning /top/restconf:



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   The client might send:

      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='/top/restconf'/>
      </XRD>

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

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

   The client might send:

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

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      Cache-Control: no-cache
      Last-Modified: Sun, 22 Apr 2016 01:00:14 GMT
      Content-Type: application/yang-data+json

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

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

   Note that any given endpoint (host:port) can only support one
   RESTCONF server, due to the root resource discovery mechanism.  This
   limits the number of RESTCONF servers that can run concurrently on a
   host, since each server must use a different port.




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3.2.  RESTCONF Media Types

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

   YANG Tree Diagram for an API Resource:

     +---- {+restconf}
           +---- data
           | ...
           +---- operations?
           | ...
           +--ro yang-library-version    string

   The "yang-api" YANG data template is defined using the "yang-data"
   extension in the "ietf-restconf" module, found in Section 8.  It
   specifies 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} root resource name used in responses representing the
   root of the "ietf-restconf" module MUST identify the "ietf-restconf"
   YANG module.  For example, a request to GET the root resource
   "/restconf" in JSON format will return a representation of the API
   resource named "ietf-restconf:restconf".

   This resource has the following child resources:









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

                           RESTCONF API Resource

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+xml

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:30 GMT
      Server: example-server
      Cache-Control: no-cache
      Content-Type: application/yang-data+xml

      <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 RPC
   operations are advertised.



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   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 access 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.

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.
   Note that the revision date for the module version found in [RFC7895]
   is used.

   Example:

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

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:30 GMT
      Server: example-server
      Cache-Control: no-cache
      Content-Type: application/yang-data+xml

      <yang-library-version
        xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library">\
        2016-06-21\
      </yang-library-version>

3.4.  Datastore Resource

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

   This resource type is an abstraction of the system's underlying
   datastore implementation.  The client uses it to edit and retrieve
   data resources, as the conceptual root 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



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   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, as described in
   Section 1.4.

   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 Prevention

   Two edit collision detection and prevention mechanisms are provided
   in RESTCONF for the datastore resource: a timestamp and an entity-
   tag.  Any change to configuration data resources updates the
   timestamp and entity tag of the datastore resource.  In addition, the
   RESTCONF server MUST return an error if the datastore is locked by an
   external source (e.g., NETCONF server).

3.4.1.1.  Timestamp

   The last change time is maintained and the "Last-Modified"
   ([RFC7232], Section 2.2) header field is returned in the response for
   a retrieval request.  The "If-Unmodified-Since" header field
   ([RFC7232], Section 3.4) 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 be for the "running" datastore.  Note
   that it is possible other protocols can cause the last-modified
   timestamp to be updated.  Such mechanisms are out of scope for this
   document.

3.4.1.2.  Entity-Tag

   The server MUST maintain a unique opaque entity-tag for the datastore
   resource and MUST return it in the "ETag" ([RFC7232], Section 2.3)
   header in the response for a retrieval request.  The client MAY use
   an "If-Match" header in edit operation requests to cause the server




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   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.  Note that each representation (e.g., XML vs. JSON)
   requires a different entity-tag.

   If the RESTCONF server is colocated with a NETCONF server, then this
   entity-tag MUST be for the "running" datastore.  Note that it is
   possible other protocols can cause the entity-tag to be updated.
   Such mechanisms are out of scope for this document.

3.4.1.3.  Update Procedure

   Changes to configuration data resources affect the timestamp and
   entity-tag for 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" URI.  This sub-tree is used
   to retrieve and edit data resources.








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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 field when it is retrieved with the GET or HEAD methods.

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

   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
   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.

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
   field 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 field can be used by a RESTCONF client in
   subsequent requests, within the "If-Match" and "If-None-Match" header
   fields.

   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.

3.5.3.  Encoding Data Resource Identifiers in the Request URI

   In YANG, data nodes can be 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.




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

   A RESTCONF data resource identifier is 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, or its parent is the datastore, then the
   module name followed by a colon character (":") MUST be 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).

   o  The leaf-list 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 and
      2.5.

   o  YANG 1.1 allows duplicate leaf-list values for non-configuration
      data.  In this case there is no mechanism to specify the exact
      matching leaf-list instance.

   o  The comma (',') character is percent-encoded [RFC3986], even
      though multiple key values are not possible for a leaf-list.  This
      is more consistent and avoids special processing rules.

   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.



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   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 and
      2.5.  The comma (',') character MUST be percent-encoded if it is
      present in the key value.

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

   o  Missing key values are not allowed, so two consecutive commas are
      interpreted as a comma, followed by a zero-length string, followed
      by a comma.  For example, "list1=foo,,baz" would be interpreted as
      a list named "list1" with 3 key values, and the second key value
      is a zero-length string.

   o  Note that non-configuration lists are not required to define keys.
      In this case, a single list instance cannot be accessed.

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

   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:




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       /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 character
   and does not need to be percent-encoded.  The value of "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.  Note that this syntax is used
   for all resources, and the API path starts with the RESTCONF root
   resource.  Data resources are required to be identified under the
   subtree "+{restconf}/data".

   An identifier is not allowed to start with the case-insensitive
   string "XML", according to YANG identifier rules.  The syntax for
   "api-identifier" and "key-value" MUST conform to the JSON identifier
   encoding rules in Section 4 of [RFC7951]: The RESTCONF root resource
   path is required.  Additional sub-resource identifiers are optional.
   The characters in a key value string are constrained, and some
   characters need to be percent-encoded, as described in Section 3.5.3.

















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

   root = string  ;; replacement string for {+restconf}

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

   module-name = identifier

   list-instance = api-identifier "=" key-value *("," key-value)

   key-value = string  ;; constrained chars are percent-encoded

   string = <an unquoted string>

   identifier  = (ALPHA / "_")
                 *(ALPHA / DIGIT / "_" / "-" / ".")


3.5.4.  Default 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
   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




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   YANG "action" statement.  It is invoked using a POST method on the
   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 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

   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.

   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
   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.



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   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.

   Examples:

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


































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


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











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   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;
             }
           }
         }
       }
     }

   }


   RPC Input Example:





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   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+xml

      <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 2016 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:

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

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

   The server might respond:



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      HTTP/1.1 204 No Content
      Date: Mon, 25 Apr 2016 11:01:00 GMT
      Server: example-server

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

      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
   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.

   The request URI is not returned in the response.  Knowledge of the
   request URI may be needed to associate the output with 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 2016 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 2016 11:10:30 GMT
      Server: example-server
      Content-Type: application/yang-data+xml

      <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 2016 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.

   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.

   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+xml

      <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 2016 11:10:30 GMT
      Server: example-server
      Content-Type: application/yang-data+xml







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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 2016 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 [RFC7895].

   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,2016-08-15/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/2016-08-15"
      }

   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/\
         2016-08-15 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.

   An event 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 the
   stream resources.





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3.9.  Errors YANG Data Template

   The "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 as 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.  RESTCONF Methods

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

   The following table shows how the RESTCONF operations relate to
   NETCONF protocol operations and for the NETCONF <edit-config>
   operation, the "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" edit operation attribute for the NETCONF <edit-config>
   RPC 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" edit operation when using a plain patch
   (see Section 4.6.1); other media-types may provide more granular
   control.

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



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   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 RESTCONF operation for any resources
   that the client is not authorized to access.

   Implementation of all methods (except PATCH [RFC5789]) 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.

   The "Accept-Patch" header field MUST be supported and returned in the
   response to the OPTIONS request, as defined in [RFC5789].

4.2.  HEAD

   The RESTCONF server MUST support the HEAD method.  The HEAD method is
   sent by the client to retrieve just the header fields (which contain
   the metadata for a resource) that would be returned for the
   comparable GET method, without the response message-body.  It is
   supported for all resources that support the GET method.

   The request MUST contain a request URI that contains at least the
   root resource.  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 RESTCONF server MUST support the GET method.  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 root
   resource.

   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
   target resource, an error response containing a "401 Unauthorized"



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   status-line SHOULD be returned.  The error-tag value "access-denied"
   is returned in this case.  A server MAY return a "404 Not Found"
   status-line, as described in section 6.5.3 in [RFC7231].  The error-
   tag value "invalid-value" is returned in this case.

   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 multiple elements are sent in a JSON
   message-body, then they MUST be sent as a JSON array.  In this case
   any timestamp or entity-tag returned in the response MUST be
   associated with the first element returned.

   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.  The
   error-tag value "invalid-value" is used in this case.  Note that a
   non-configuration list is not required to defined any keys.  In this
   case, retrieval of a single list instance is not possible.

   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.  The error-tag
   value "invalid-value" is used in this case.

   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.  The error-tag value "operation-not-supported" is used
   in this case.

   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 header fields 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 header fields for an XML
   representation of the a specific "album" resource:





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

   The server might respond:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:02:40 GMT
      Server: example-server
      Content-Type: application/yang-data+xml
      Cache-Control: no-cache
      ETag: "a74eefc993a2b"
      Last-Modified: Mon, 23 Apr 2016 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>

   Refer to Appendix D.1 for more resource retrieval examples.

4.4.  POST

   The RESTCONF server MUST support the POST method.  The POST method is
   sent by the client to create a data resource or invoke an operation
   resource.  The server uses the target resource 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



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   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 field
   identifying the child resource that was created MUST be present in
   the response in this case.

   If the data resource already exists, then the POST request MUST fail
   and a "409 Conflict" status-line MUST be returned.  The error-tag
   value "resource-denied" is used in this case.

   If the user is not authorized to create the target resource, an error
   response containing a "403 Forbidden" status-line SHOULD be returned.
   The error-tag value "access-denied" is used in this case.  A server
   MAY return a "404 Not Found" status-line, as described in section
   6.5.3 in [RFC7231].  The error-tag value "invalid-value" is used in
   this case.  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:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      Location: https://example.com/restconf/data/\
          example-jukebox:jukebox
      Last-Modified: Mon, 23 Apr 2016 17:01:00 GMT
      ETag: "b3a3e673be2"

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





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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 SHOULD be
   returned.  The error-tag value "access-denied" is used in this case.
   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:

   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 2016 17:50:00 GMT
      Server: example-server

4.5.  PUT

   The RESTCONF server MUST support the PUT method.  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




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   resource, or the server MUST return "400 Bad Request" status-line.
   The error-tag value "invalid-value" is used in this case.

   Both the POST and PUT methods can be used to create data resources.
   The difference is that for POST, the client does not provide the
   resource identifier for the resource that will be created.  The
   target resource for the POST method for resource creation is the
   parent of the new resource.  The target resource for the PUT method
   for resource creation is the new resource.

   The PUT method MUST be supported for data and datastore resources.  A
   PUT on the datastore resource is used to replace the entire contents
   of the datastore.  A PUT on a data resource only replaces that data
   resource within the datastore.

   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.  The error-tag value "access-denied" is used in
   this case.

    A server MAY return a "404 Not Found" status-line, as
   described in section 6.5.3 in ^RFC7231^.
   The error-tag value "invalid-value" is used in this case.
   All other error responses are handled according to
   the procedures defined in ^error-reporting^.

   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 key
   leaf values in message-body representation MUST be the same as the
   key leaf values in the request URI.  The PUT method MUST NOT be used
   to change the key leaf values for a data resource instance.

   Example:

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




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   To replace the "album" resource contents, the client might send as
   follows:

      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 2016 17:04:00 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2016 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+xml

      <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>

   Refer to Appendix D.2.4 for an example using the PUT method to
   replace the contents of the datastore resource.

4.6.  PATCH

   The RESTCONF server MUST support the PATCH method for a plain patch,
   and MAY support additional media types.  The PATCH media types
   supported by a server can be discovered by the client by sending an



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   OPTIONS request, and examining the Accept-Patch header field in the
   response.  (see Section 4.1).

   RESTCONF uses the HTTP PATCH method defined in [RFC5789] to provide
   an extensible framework for resource patching mechanisms.  Each patch
   mechanism needs a unique media type.

   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].  The error-tag value "invalid-value" is
   used in this case.  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+xml" 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 method.

   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 key
   leaf values in message-body representation MUST be the same as the
   key leaf values in the request URI.  The PATCH method MUST NOT be
   used to change the key leaf values for a data resource instance.




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   After the plain patch is processed by the server a response will be
   returned to the client, as specified in Section 4.6.

   Example:

   To replace just the "year" field in the "album" resource (instead of
   replacing the entire resource with the PUT method), the client might
   send a plain patch as follows.

      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+xml

      <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 2016 17:49:30 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2016 17:49:30 GMT
      ETag: "b2788923da4c"

4.7.  DELETE

   The RESTCONF server MUST support the DELETE method.  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.  The error-tag value "access-denied" is returned in this
   case.  A server MAY return a "404 Not Found" status-line, as
   described in section 6.5.3 in [RFC7231].  The error-tag value
   "invalid-value" is returned in this case.  All other error responses
   are handled according to the procedures defined in Section 7.

   If the target resource represents a configuration leaf-list or list
   data node, then it MUST represent a single YANG leaf-list or list
   instance.  The server MUST NOT use the DELETE method to delete more
   than one such instance.

   Example:




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   To delete the "album" resource with the key "Wasting Light", 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 2016 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.  The
      error-tag value "invalid-value" is returned in this case.

   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.  The error-tag value
      "invalid-value" is returned in this case.
















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

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






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   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 limit the depth of subtrees returned
   by the server.  Data nodes with a depth value greater than the
   "depth" parameter are not returned in a response for a GET method.

   The requested data node has a depth level of '1'.  If the "fields"
   parameter (Section 4.8.3) is used to select descendant data nodes,
   then these nodes and all their ancestor nodes have a depth value of
   1.  (This has the effect of including the nodes specified by the
   fields, even if the "depth" value is less than the actual depth level
   of the specified fields.)  Any other child node has 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.

   The server will return a message-body representing the target
   resource, with descendant nodes pruned as specified in the




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   "fields-expr" value.  The server does not return a set of separate
   sub-resources.

   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 '('.

   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 an event stream
   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 [XPath], and
   is evaluated in the following context:



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   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.

   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.






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   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.

   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



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   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, anf 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.

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, and 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.





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

   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].  Metadata is reported by the server as
   specified in Section 5.3.  The XML encoding for the "default"
   attribute sent by the server for default nodes is defined in section
   6 of [RFC6243].  The JSON encoding for the "default" attribute MUST
   use the same values as defined in [RFC6243], but encoded according to
   the rules in [RFC7952].  The module name "ietf-netconf-with-defaults"
   MUST be used for the "default" attribute.

   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.





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   Since the server does not report the "also-supported" parameter as
   described in section 4.3 of [RFC6243], it is possible that some
   values for the "with-defaults" parameter will not be supported.  If
   the server does not support the requested value of the
   "with-defaults" parameter, the server MUST return a response with a
   "400 Bad Request" status-line.  The error-tag value "invalid-value"
   is used in this case.

5.  Messages

   The RESTCONF protocol uses HTTP 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>

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

          M       M        O        O

       M=mandatory, O=optional

       where:

         <OP> is the HTTP method
         <restconf> is the RESTCONF root resource
         <path> is the Target Resource URI
         <query> is the query parameter list

   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.






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   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 RESTCONF 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 and 2.5.

   Note that the fragment component not used by the RESTCONF protocol.
   The fragment is excluded from the target URI by a server, as
   described in section 5.1 of [RFC7230].

   When new resources are created by the client, a "Location" header
   field 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 a RESTCONF operation is a resource.  The "path" field
   in the request URI represents the target resource for the RESTCONF
   operation.

   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 one of either XML or JSON encoding.  A server MAY support
   both XML and JSON encoding.  A client will need to support both XML
   and JSON to interoperate with all RESTCONF servers.



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   XML encoding rules for data nodes are defined in [RFC7950].  The same
   encoding rules are used for all XML content.  JSON encoding rules are
   defined in [RFC7951].  Additional JSON encoding rules for metadata
   are defined in [RFC7952].  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 field.  This field MUST be present if a message-body is
   sent by the client.

   The server MUST support the "Accept" header field and "406 Not
   Acceptable" status-line, as defined in [RFC7231].  The response
   output content encoding formats that the client will accept are
   identified with the Accept header field 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 field.  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 support retrieval of 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.

   With the XML encoding, the metadata is encoded as attributes in XML,
   according to section 3.3 of [W3C.REC-xml-20081126].  With the JSON
   encoding, the metadata is encoded as specified in [RFC7952].

   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 .





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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+xml

   The server might respond as follows.

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      Content-Type: application/yang-data+xml

      <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.  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.
















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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      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 field 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 MUST include a "Cache-Control" header field 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" header fields 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" header fields, 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 header fields, which SHOULD include the




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   "ETag" and "Last-Modified" header fields, if this metadata is
   maintained for the target resource.

   Note that the way that access control is applied to data resources
   the values in the Last-Modified and ETag headers maintained for a
   data resource may not be reliable, as described in Section 4.3.

6.  Notifications

   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 method 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 method 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+xml

   The server might send the following response:

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




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      <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\
            </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>







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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".

   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 event 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+xml

   The server might send the following response:

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

      <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:





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      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" event stream defined in
   section 3.2.3 of [RFC5277].  The notification messages for this
   stream are encoded in XML.

   The server MAY support additional streams which represent the
   semantic content of the NETCONF event stream, but using a
   representation with a different media type.

   The server MAY support the "start-time", "stop-time", and "filter"
   query parameters, defined in Section 4.8.  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 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] using
   the XML namespace as defined in the XSD as follows:

     urn:ietf:params:xml:ns:netconf:notification:1.0

   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 "eventTime"
   node is defined within the same XML namespace as the "notification"
   element.  It is defined to be within the "ietf-restconf" module
   namespace for JSON encoding purposes.

   The name and namespace of the payload element are determined by the
   YANG module containing the notification-stmt representing the
   notification message.

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




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

       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:netconf:notification:1.0">
      data:    <eventTime>2013-12-21T00:01:00Z</eventTime>
      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:     "eventTime" : "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:







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      XML:

      data: <notification xmlns="urn:ietf:params:xml:ns:netconf:notif\
      ication:1.0"><eventTime>2013-12-21T00:01:00Z</eventTime><event \
      xmlns="http://example.com/event/1.0"><event-class>fault</event-\
      class><reportingEntity><card>Ethernet0</card></reporting-entity>\
      <severity>major</severity></event></notification>

      JSON:

      data: {"ietf-restconf:notification":{"eventTime":"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 field "Last-Event-Id".  RESTCONF servers that do send
   the "id" field SHOULD support the "start-time" 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 error information that NETCONF error responses
   contain in the <rpc-error> element is adapted for use in RESTCONF,
   and an <errors> data tree 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
   from the NETCONF <error-tag> value to 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.











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               +-------------------------+-----------------+
               | error-tag               | status code     |
               +-------------------------+-----------------+
               | in-use                  | 409             |
               | invalid-value           | 400, 404 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           | 401, 403        |
               | lock-denied             | 409             |
               | resource-denied         | 409             |
               | rollback-failed         | 500             |
               | data-exists             | 409             |
               | data-missing            | 409             |
               | operation-not-supported | 405 or 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 data template within the "ietf-restconf" module,
   found in Section 8.  The Content-Type of this response message MUST
   be "application/yang-data", plus optionally a structured syntax name
   suffix.

   The client SHOULD specify the desired encoding(s) for response
   messages by specifying the appropriate media-type(s) in the Accept
   header.  If the client did not specify an Accept header, then the
   same structured syntax name suffix used in 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+xml" 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.



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   YANG Tree Diagram for <errors> data:

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

   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 field is used to specify the desired encoding for
   the error message.  There would be no response message-body content
   if this operation was successful.

      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 2016 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"
            }
          ]
        }
      }





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

   The client might send:

      POST /restconf/data/example-jukebox:jukebox HTTP/1.1
      Host: example.com

   The server might respond:

      HTTP/1.1 409 Conflict
      Date: Mon, 23 Apr 2016 17:11:00 GMT
      Server: example-server
      Content-Type: application/yang-data+xml

      <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" URI).

   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@2016-08-15.yang"

   module ietf-restconf {



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     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>

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

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

        Author:   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



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     // Note: extracted from draft-ietf-netconf-restconf-17.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2016-08-15 {
       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
          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 a yang-data extension
          specify the generic syntax for the specific YANG data
          template, whose name is the argument of the yang-data
          extension statement.

          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 MUST contain data definition statements
          that result in exactly one container data node definition.
          An instance of a YANG data template can thus be translated
          into an XML instance document, whose top-level element
          corresponds to the top-level container.

          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.




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          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 are constrained
          when used within a yang-data-resource extension statement.

            - 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.";




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

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

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

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

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

           leaf error-message {



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             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 grouping representing the RESTCONF
          root resource.";

       container restconf {
         description
           "Conceptual container representing the RESTCONF
            root resource.";

         container data {
           description
             "Container representing the datastore resource.
              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 which are defined as top-level data nodes
              from the YANG modules advertised by the server in
              the ietf-yang-library module.";
         }

         container operations {
           description
             "Container for all operation resources.

              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:



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                 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
                   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>







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9.  RESTCONF Monitoring

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

   YANG tree diagram for "ietf-restconf-monitoring" module:

      +--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 field 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 field 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.






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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       | Sectio | URI                                         |
   |            | n      |                                             |
   +------------+--------+---------------------------------------------+
   | 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 "basic-mode" defaults handling mode that is
   used by the server for processing default leafs in requests for data
   resources.  This protocol capability URI MUST be supported by the
   server, and MUST be listed in the "capability" leaf-list in
   Section 9.3.

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

                     RESTCONF defaults capability URI

   The URI MUST contain a query parameter named "basic-mode" with one of
   the values listed below:






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

   The "basic-mode" definitions are specified in the "With-Defaults
   Capability for NETCONF" [RFC6243].

   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].

   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 streams
   supported by the server.  The server MAY omit this container if no
   event 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.




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   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@2016-08-15.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";

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

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

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

        Author:   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.";




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

     // RFC Ed.: remove this note
     // Note: extracted from draft-ietf-netconf-restconf-17.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2016-08-15 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: RESTCONF Protocol.";
     }

     container restconf-state {
       config false;
       description
         "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.";
           }



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

           leaf replay-support {
             type boolean;
             default false;
             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.";
           }

           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.



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                  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.";
             }
           }
         }
       }
     }

   }

   <CODE ENDS>

10.  YANG Module Library

   The "ietf-yang-library" module defined in [RFC7895] 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/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 [RFC7895].

   Note that there are no protocol accessible objects in the
   "ietf-restconf" module to implement, but it is possible that a server
   will list the "ietf-restconf" module in the YANG library if it is
   imported (directly or indirectly) by an implemented module.

11.  IANA Considerations








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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

   `

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






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11.3.  Media Types

11.3.1.  Media Type application/yang-data+xml

      Type name: application

      Subtype name: yang-data+xml

      Required parameters: None

      Optional parameters: None

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

     // 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: Fragment identifiers for
         this type are not defined.  All YANG data nodes are



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         accessible as resources using the path in the request URI.

      Additional information:

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

     // 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

11.3.2.  Media Type application/yang-data+json

      Type name: application

      Subtype name: yang-data+json

      Required parameters: None

      Optional parameters: None

      Encoding considerations: 8-bit
         Each conceptual YANG data node is encoded according to
         [RFC7951]. A data annotation is encoded according to
         [RFC7952].

     // 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.



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      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 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): None
        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].



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

      Provisional registration? (standards tree only): no

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





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11.5.  Registration of "restconf" URN sub-namespace

   IANA has registered a new URN sub-namespace within the IETF URN Sub-
   namespace for Registered Protocol Parameter Identifiers defined in
   [RFC3553].

      Registry Name: restconf

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

      Repository: RESTCONF Capability URNs registry (Section 11.4)

      Index value:  Sub-parameters MUST be specified in UTF-8, using
          standard URI encoding where necessary.

12.  Security Considerations

   Section 2.1 states "A RESTCONF server MUST support the TLS protocol
   [RFC5246]".  This language leaves open the possibility that a
   RESTCONF server might also support future versions of the TLS
   protocol.  Of specific concern, TLS 1.3 [I-D.ietf-tls-tls13]
   introduces support for 0-RTT handshakes that can lead to security
   issues for REST APIs, as described in the Appendix of the TLS 1.3
   specification.  It is therefore RECOMMENDED that RESTCONF servers do
   not support 0-RTT at all (not even for idempotent requests) until an
   update to this RFC guides otherwise.

   Section 2.5 recommends TLS client certificate based authentication,
   but allows the use of any authentication scheme defined in the HTTP
   Authentication Scheme Registry.  Implementations need to be aware
   that the strength of these methods vary greatly, and that some may be
   considered experimental.  Selection of any of these schemes SHOULD be
   performed after reading the Security Considerations section of the
   RFC associated with the scheme's registry entry.

   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)
   [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.

   The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement
   secure transport is TLS [RFC5246].  The RESTCONF protocol uses the
   NETCONF access control model [RFC6536], which provides the means to



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   restrict access for particular RESTCONF users to a preconfigured
   subset of all available RESTCONF 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, except the
   "ietf-restconf-monitoring" module.  Security considerations for the
   other modules manipulated by RESTCONF can be found in the documents
   defining those YANG modules.

   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.  There are many patterns of attack that have
   been observed through operational practice with existing management
   interfaces.  It would be wise for implementers to research them, and
   take them into account when implementing this protocol.

   Different environments may well allow different rights prior to and
   then after authentication.  When a RESTCONF 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.

   A RESTCONF server implementation SHOULD attempt to prevent system
   disruption due to excessive resource consumption required to fulfill
   edit requests via the POST, PUT, and PATCH methods.  It may be
   possible to construct an attack on such a RESTCONF server, which
   attempts to consume all available memory or other resource types.

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.

   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



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   Uveges, Randy Presuhn, Sue Hares, Mark Nottingham, Benoit Claise,
   Dale Worley, and Lionel Morand.

   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

   [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.

   [RFC3553]  Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An
              IETF URN Sub-namespace for Registered Protocol
              Parameters", BCP 73, RFC 3553, DOI 10.17487/RFC3553, June
              2003, <http://www.rfc-editor.org/info/rfc3553>.

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

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

   [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.




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   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988, October 2010.

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

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

   [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.

   [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.





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

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <http://www.rfc-editor.org/info/rfc7525>.

   [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>.

   [RFC7895]  Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", RFC 7895, June 2016.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <http://www.rfc-editor.org/info/rfc7950>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <http://www.rfc-editor.org/info/rfc7951>.

   [RFC7952]  Lhotka, L., "Defining and Using Metadata with YANG",
              RFC 7952, DOI 10.17487/RFC7952, August 2016,
              <http://www.rfc-editor.org/info/rfc7952>.

   [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-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>.




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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-12 (work in
              progress), October 2016.

   [I-D.ietf-tls-tls13]
              Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", draft-ietf-tls-tls13-18 (work in progress),
              October 2016.

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

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 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.  v17 to v18

   o  addressed IESG review comments and clarifications

   o  addressed Alexey's DISCUSS items

   o  made Cache-Control MUST support, not SHOULD support

   o  add example for PUT on a datastore

   o  add IANA section for "restconf" URN sub-namespace

   o  clarify media type file extensions

A.2.  v16 to v17

   o  various clarifications from NETCONF WG mailing list

   o  updated YANG 1.1 and YANG/JSON references to RFC numbers

   o  fixed notification namespace and eventTime name bug





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   o  changed media type application/yang-data-xml to application/yang-
      data+xml

   o  update fragment identifier considerations section for application/
      yang-data+xml

   o  clarify HTTP version requirements

A.3.  v15 to v16

   o  changed media type application/yang-data to application/yang-data-
      xml

   o  changed header to header field

   o  added linewrap convention in terminology and applied in many
      examples

   o  clarified DELETE for leaf-list and list

   o  clarified URI format for lists without keys or duplicate leaf-
      lists

   o  added 'yang-data extension' term and clarified 'YANG data
      template' term

   o  clarified that the fragment component is not part of the request
      URI, per HTTP

   o  clarified request URI "api-path" syntax

   o  clarified many examples

A.4.  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

   o  added clarifications based on ops-dir review by Lionel Morand

   o  clarified PUT and POST differences for creating a data resource

   o  clarify PUT for a datastore resource



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   o  added clarifications from Gen-Art review by Robert Sparks

   o  clarified terminology in many places

A.5.  v13 - v14

   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




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   o  added example for 'edit a data resource'

   o  added term 'notification replay' from RFC 5277

   o  clarified unsupported encoding format error handling

   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








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A.6.  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.7.  v11 - v12

   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.8.  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




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   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

   o  clarify ordered-by user terminology

   o  fixed JSON example in D.1.1

A.9.  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




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   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

   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



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   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

   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.10.  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.11.  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




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A.12.  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.

   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.13.  v05 - v06

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

A.14.  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



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   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

A.15.  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.16.  v02 - v03

   o  added collection resource

   o  added "page" query parameter capability




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   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

   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.17.  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



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   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

A.18.  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"



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A.19.  bierman:restconf-04 to ietf:restconf-00

   o  updated open issues section

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       instance-identifier
         +--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 "2016-08-15" {
        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 instance-identifier;
              mandatory true;
              description
                "Song identifier. Must identify an instance of
                 /jukebox/library/artist/album/song/name.";
            }
          }
        }

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

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

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



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            description "Song number in playlist to play";
          }
        }
      }
   }


Appendix D.  RESTCONF Message Examples

   The examples within this document use the normative YANG module
   "ietf-restconf" defined in Section 8 and the non-normative example
   YANG module "example-jukebox" 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 root resource:

      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
   root resource "/restconf".

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

   The server might respond as follows:








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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      Content-Type: application/yang-data+json

      {
        "ietf-restconf:restconf" : {
          "data" : {},
          "operations" : {},
          "yang-library-version" : "2016-06-21"
        }
      }

   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+xml

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

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      Cache-Control: no-cache
      Content-Type: application/yang-data+xml

      <restconf xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
        <data/>
        <operations/>
        <yang-library-version>2016-06-21</yang-library-version>
      </restconf>

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



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   The server might respond as follows:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      Cache-Control: no-cache
      Last-Modified: Sun, 22 Apr 2016 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",
              "revision" : "2016-06-21",
              "schema" : "https://example.com/modules/\
                ietf-yang-library/2016-06-21",
              "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",



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              "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:

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

   The server might respond as follows:

      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:02:00 GMT
      Server: example-server
      Cache-Control: no-cache
      Last-Modified: Sun, 22 Apr 2016 01:00:14 GMT
      Content-Type: application/yang-data+xml










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      <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

   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"
          }
        ]
      }




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   If the resource is created, the server might respond as follows:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2016 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 2016 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:

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

      <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:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2016 17:03:00 GMT
      Server: example-server
      Location: https://example.com/restconf/data/\
          example-jukebox:jukebox/library/artist=Foo%20Fighters/\
          album=Wasting%20Light
      Last-Modified: Mon, 23 Apr 2016 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.  After the previous request, the client has cached the
   "Last-Modified" header and the Location header from the response to
   provide in the following request to patch an "album" list entry with
   key value "Wasting Light".  Only the "genre" field is being updated.










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      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 2016 17:03:00 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 2016 19:01:00 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2016 17:45:00 GMT
      ETag: "b34aed893a4c"

D.2.3.  Edit a Datastore Resource

   In this example, assume there is a top-level data resource named
   "system" from the example-system module, and this container has a
   child leaf called "enable-jukebox-streaming":

      container system {
        leaf enable-jukebox-streaming {
          type boolean;
        }
      }

   In this example PATCH is used by the client to modify 2 top-level
   resources at once, in order to enable jukebox streaming and add an
   "album" sub-resource to each of 2 "artist" resources:

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













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      <data xmlns="urn:ietf:params:xml:ns:yang:ietf-restconf">
        <system xmlns="http://example.com/ns/example-system">
          <enable-jukebox-streaming>true</enable-jukebox-streaming>
        </system>
        <jukebox xmlns="http://example.com/ns/example-jukebox">
          <library>
            <artist>
              <name>Foo Fighters</name>
              <album>
                <name>One by One</name>
                <year>2012</year>
              </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.  Replace a Datastore Resource

   In this example, the entire configuration datastore contents are
   being replaced.  Any child nodes not present in the <data> element
   but present in the server will be deleted.

      PUT /restconf/data HTTP/1.1
      Host: example.com
      Content-Type: application/yang-data+xml


















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      <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>One by One</name>
                <year>2012</year>
              </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.2.5.  Edit a Data Resource

   In this example, the client modifies one data node by adding an
   "album" sub-resource by sending a PATCH for the data resource:

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

      <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.





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   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 {
           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:
























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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 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".

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

   The server might respond:















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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:11:30 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2016 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:















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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:11:30 GMT
      Server: example-server
      Cache-Control: no-cache
      Content-Type: application/yang-data+json

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

D.3.2.  "depth" Parameter

   The "depth" parameter is used to limit the number of levels of 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".

      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



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      Date: Mon, 23 Apr 2016 17:11:30 GMT
      Server: example-server
      Cache-Control: no-cache
      Content-Type: application/yang-data+json

      {
        "example-jukebox:jukebox" : {
          "library" : {
            "artist" : [
              {
                "name" : "Foo Fighters",
                "album" : [
                  {
                    "name" : "Wasting Light",
                    "genre" : "example-jukebox:alternative",
                    "year" : 2011,
                    "song" : [
                      {
                        "name" : "Wasting Light",
                        "location" :
                          "/media/foo/a7/wasting-light.mp3",
                        "format" : "MP3",
                        "length" : 286
                      },
                      {
                        "name" : "Rope",
                        "location" : "/media/foo/a7/rope.mp3",
                        "format" : "MP3",
                        "length" : 259
                      }
                    ]
                  }
                ]
              }
            ]
          },
          "playlist" : [
            {
              "name" : "Foo-One",
              "description" : "example playlist 1",
              "song" : [
                {
                  "index" : 1,
                  "id" : "/example-jukebox:jukebox/library\
                     /artist[name='Foo Figthers']\
                     /album[name='Wasting Light']\
                     /song[name=Rope']"
                },



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                {
                  "index" : 2,
                  "id" : "/example-jukebox:jukebox/library\
                     /artist[name='Foo Figthers']\
                     /album[name='Wasting Light']\
                     /song[name=Bridge Burning']"
                }
              ]
            }
          ],
          "player" : {
            "gap" : 0.5
          }
        }
      }

   Example 2: depth=1

   To determine if 1 or more resource instances exist for a given target
   resource, the value one 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 2016 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:




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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:11:30 GMT
      Server: example-server
      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-restconf-monitoring below
   to the date in the published ietf-restconf-monitoring YANG module,
   and remove this note.]








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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 17:01:00 GMT
      Server: example-server
      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" : "2016-06-21"
              },
              {
                "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:











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      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[name='Foo Figthers']\
                /album[name='Wasting Light']\
                /song[name=Rope']"
           }
         ]
      }

   Response from server:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2016 13:01:20 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2016 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 entry in the
   "Foo-One" playlist after the first song.

   Request from client:


















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      POST /restconf/data/example-jukebox:jukebox/\
          playlist=Foo-One?insert=after&point=\
          %2Fexample-jukebox%3Ajukebox\
          %2Fplaylist%3DFoo-One%2Fsong%3D1 HTTP/1.1
      Host: example.com
      Content-Type: application/yang-data+json

      {
        "example-jukebox:song" : [
           {
             "index" : 2,
             "id" : "/example-jukebox:jukebox/library\
                /artist[name='Foo Figthers']\
                /album[name='Wasting Light']\
                /song[name=Bridge Burning']"
           }
         ]
      }

   Response from server:

      HTTP/1.1 201 Created
      Date: Mon, 23 Apr 2016 13:01:20 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2016 13:01:20 GMT
      Location: https://example.com/restconf/data/\
          example-jukebox:jukebox/playlist=Foo-One/song=2
      ETag: "abcada438af"

D.3.6.  "filter" Parameter

   The following URIs show some examples of notification filter
   specifications:


















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      // 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

   The following URI shows an example of the "start-time" query
   parameter:

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

D.3.8.  "stop-time" Parameter

   The following URI shows an example of the "stop-time" query
   parameter:

      // start-time = 2014-10-25T10:02:00Z
      // stop-time = 2014-10-25T12:31:00Z
      GET /mystreams/NETCONF?start-time=2014-10-25T10%3A02%3A00Z\
         &stop-time=2014-10-25T12%3A31%3A00Z






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D.3.9.  "with-defaults" Parameter

   Assume the server implements the module "example" defined in
   Appendix A.1 of [RFC6243].  Assume the server's datastore is 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 2016 17:01:00 GMT
      Server: example-server
      Content-Type: application/yang-data+json

      {
        "example:interface" : [
          {
            "name" : "eth1",
            "status" : "up"
          }
        ]
      }

   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.









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      HTTP/1.1 200 OK
      Date: Mon, 23 Apr 2016 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


   Kent Watsen
   Juniper Networks

   Email: kwatsen@juniper.net















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