Network Working Group                                         A. Bierman
Internet-Draft                                                 YumaWorks
Intended status: Standards Track                            M. Bjorklund
Expires: June September 17, 2016                               Tail-f Systems
                                                               K. Watsen
                                                        Juniper Networks
                                                       December 15, 2015
                                                          March 16, 2016

                         YANG Patch Media Type
                    draft-ietf-netconf-yang-patch-07
                    draft-ietf-netconf-yang-patch-08

Abstract

   This document describes a method for applying patches to NETCONF
   configuration datastores using data defined with the YANG data
   modeling language.

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 June September 17, 2016.

Copyright Notice

   Copyright (c) 2015 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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
       1.1.1.  NETCONF . . . . . . . . . . . . . . . . . . . . . . .   3
       1.1.2.  HTTP  . . . . . . . . . . . . . . . . . . . . . . . .   3   4
       1.1.3.  YANG  . . . . . . . . . . . . . . . . . . . . . . . .   4
       1.1.4.  RESTCONF  . . . . . . . . . . . . . . . . . . . . . .   4   5
       1.1.5.  YANG Patch  . . . . . . . . . . . . . . . . . . . . .   5
       1.1.6.  Tree Diagrams . . . . . . . . . . . . . . . . . . . .   5
   2.  YANG Patch  . . . . . . . . . . . . . . . . . . . . . . . . .   5   6
     2.1.  Target Resource . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  yang-patch Input  . . . . . . . . . . . . . . . . . . . .   6
     2.3.  yang-patch-status Output  . . . . . . . . . . . . . . . .   7
     2.4.  Target Data Node  . . . . . . . . . . . . . . . . . . . .   7   8
     2.5.  Edit Operations . . . . . . . . . . . . . . . . . . . . .   8
     2.6.  Successful Edit Response Handling . . . . . . . . . . . .   9
     2.7.  Error Handling  . . . . . . . . . . . . . . . . . . . . .   8
     2.7.   9
     2.8.  yang-patch RESTCONF Capability  . . . . . . . . . . . . .   9
   3.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .   9
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17  18
     4.1.  YANG Module Registry  . . . . . . . . . . . . . . . . . .  18
     4.2.  application/yang.patch Media Types  . . . . . . . . . . .  18  19
     4.3.  application/yang.patch-status Media Types . . . . . . . .  18  19
     4.4.  RESTCONF Capability URNs  . . . . . . . . . . . . . . . .  19  20
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  19  20
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .  19  20
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  20  21
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  21  22
     B.1.  v07 to v08  . . . . . . . . . . . . . . . . . . . . . . .  22
     B.2.  v06 to v07  . . . . . . . . . . . . . . . . . . . . . . .  21
     B.2.  22
     B.3.  v05 to v06  . . . . . . . . . . . . . . . . . . . . . . .  21
     B.3.  22
     B.4.  v04 to v05  . . . . . . . . . . . . . . . . . . . . . . .  21
     B.4.  23
     B.5.  v03 to v04  . . . . . . . . . . . . . . . . . . . . . . .  21
     B.5.  23
     B.6.  v02 to v03  . . . . . . . . . . . . . . . . . . . . . . .  22
     B.6.  23
     B.7.  v01 to v02  . . . . . . . . . . . . . . . . . . . . . . .  22
     B.7.  23
     B.8.  v00 to v01  . . . . . . . . . . . . . . . . . . . . . . .  22
     B.8.  24
     B.9.  bierman:yang-patch-00 to ietf:yang-patch-00 . . . . . . .  23  24

   Appendix C.  Open Issues  . . . . . . . . . . . . . . . . . . . .  23  25
   Appendix D.  Example YANG Module  . . . . . . . . . . . . . . . .  23  25
     D.1.  YANG Patch Examples . . . . . . . . . . . . . . . . . . .  24  26
       D.1.1.  Add Resources: Error  . . . . . . . . . . . . . . . .  24  26
       D.1.2.  Add Resources: Success  . . . . . . . . . . . . . . .  27  29
       D.1.3.  Move list entry example . . . . . . . . . . . . . . .  29  30
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  29  31

1.  Introduction

   There is a need for standard mechanisms to patch NETCONF [RFC6241] datastores defined
   in [RFC6241], which contain conceptual data that conforms to schema
   specified with YANG [RFC6020]. [I-D.ietf-netmod-rfc6020bis].  An "ordered edit
   list" approach is needed to provide client developers with a simpler edit request
   format that can be more efficient and also allow more
   precise client control of the transaction edit procedure than existing
   mechanisms.

   This document defines a media type for a YANG-based editing mechanism
   that can be used with the HTTP PATCH method [RFC5789].  YANG Patch is
   designed to support the RESTCONF protocol, defined in
   [I-D.ietf-netconf-restconf].

   It may be possible to use YANG Patch with other protocols besides
   RESTCONF.  This is outside the scope of this document.  It may be
   possible to use YANG Patch with datastore types other than a
   configuration datastore.  This is outside the scope of this document.

1.1.  Terminology

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

1.1.1.  NETCONF

   The following terms are defined in [RFC6241]:

   o  client

   o  configuration data

   o  datastore

   o  configuration datastore

   o  protocol operation
   o  running configuration datastore

   o  server

   o  state data

   o  user

1.1.2.  HTTP

   The following terms are defined in [RFC2616]:

   o  entity tag

   o  fragment

   o  header line

   o  message body

   o  method

   o  path

   o  query

   o  request URI

   o  response body

1.1.3.  YANG

   The following terms are defined in [RFC6020]: [I-D.ietf-netmod-rfc6020bis]:

   o  container

   o  data node

   o  key leaf

   o  leaf

   o  leaf-list

   o  list

   o  presence container (or P-container)
   o  RPC operation (now called protocol operation)

   o  non-presence container (or NP-container)

   o  ordered-by system

   o  ordered-by user

1.1.4.  RESTCONF

   The following terms are defined in [I-D.ietf-netconf-restconf]:

   o  data resource

   o  datastore resource

   o  patch

   o  RESTCONF capability

   o  target resource

1.1.5.  YANG Patch

   The following terms are used within this document:

   o  YANG Patch: a conceptual edit request using the "yang-patch" YANG
      container, defined in Section 3.  In HTTP, refers to a PATCH
      method where the media type is "application/yang.patch+xml" or
      "application/yang.patch+json".

   o  YANG Patch Status: a conceptual edit status response using the
      YANG "yang-patch-status" container, defined in Section 3.  In
      HTTP, refers to a response message for a PATCH method, where the
      message body is identified by the media type "application/
      yang.patch-status+xml" or "application/yang.patch-status+json".

1.1.6.  Tree Diagrams

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

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

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

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

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

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

2.  YANG Patch

   A "YANG Patch" is an ordered list of edits that are applied to the
   target datastore by the server.  The specific fields are defined in
   the YANG module in Section 3.

   For RESTCONF, the YANG Patch operation is invoked by the client by
   sending a PATCH method request with the YANG Patch media type.  A
   message body representing the YANG Patch input parameters MUST be
   provided.

   The RESTCONF server MUST return the Accept-Patch header in an OPTIONS
   response, as specified in [RFC5789], which includes the media type
   for YANG Patch.

   Example:

   Accept-Patch: application/yang.patch

   A YANG Patch can be encoded in XML format according to
   [W3C.REC-xml-20081126].  It can also be encoded in JSON, according to
   "JSON Encoding of Data Modeled with YANG"
   [I-D.ietf-netmod-yang-json].  If any meta-data needs to be sent in a
   JSON message, it is encoded according to "Defining and Using Metadata
   with YANG" [I-D.ietf-netmod-yang-metadata].

   Example:

   Accept-Patch: application/yang.patch

2.1.  Target Resource

   The YANG Patch operation uses a conceptual root within a NETCONF
   configuration datastore to identity the patch point for RESTCONF target resource URI to
   identify the edit
   operation. resource that will be patched.  This root can be the
   datastore resource itself, i.e., "{+restconf}/data", or 1 or more it can be a
   configuration data
   nodes resource within the datastore.

   For RESTCONF, the datastore resource, e.g.,
   {+restconf/data/ietf-interfaces:interfaces".

   Each edit with a YANG Patch identifies a target resource is derived from data node for the request URI.
   associated edit.  This is described in Section 2.4.

2.2.  yang-patch Input
   A YANG patch is optionally identified by a unique "patch-id" and it
   may have an optional comment.  A patch is an ordered collection of
   edits.  Each edit is identified by an "edit-id" and it has an edit
   operation (create, delete, insert, merge, move, replace, remove) that
   is applied to the target resource.  Each edit can be applied to a
   sub-resource "target" within the target resource.  If the operation
   is "insert" or "move", then the "where" parameter indicates how the
   node is inserted or moved.  For values "before" and "after", the
   "point" parameter specifies the data node insertion point.

   A data element representing the YANG Patch is sent by the client to
   specify the edit operation request.  When used with the HTTP PATCH
   method, this data is identified by the YANG Patch media type.

   YANG Tree Diagram For "yang-patch" Container

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

2.3.  yang-patch-status Output

   A data element representing the YANG Patch Status is returned to the
   client to report the detailed status of the edit operation.  When
   used with the HTTP PATCH method, this data is identified by the YANG
   Patch Status media type, and the syntax specification is defined in
   Section 3.

   YANG Tree Diagram For "yang-patch-status" Container:

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

2.4.  Target Data Node

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

   If the target resource specified in the request URI identifies a
   datastore resource, then the path string in the "target" leaf is
   treated as an absolute path expression. expression identifying the target data
   node for the corresponding edit.  The first node specified in the
   "target" leaf is a top-level data node defined within a YANG module.
   The "target" leaf MUST NOT contain a single forward slash "/", since
   this would identify the datastore resource, not a data resource.

   If the target resource specified in the request URI identifies a
   configuration data resource, then the path string in the "target"
   leaf is treated as a relative path expression.  The first node
   specified in the "target" leaf is a child configuration data node of
   the data node associated with the target resource.  If the "target"
   leaf contains a single forward slash "/", then the target data node
   is the target resource data node.

2.5.  Edit Operations

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

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

                        YANG Patch Edit Operations

2.6.  Successful Edit Response Handling

   If a YANG Patch is completed without errors, the server MUST return a
   "200 OK" status-line, and a response message-body containing a
   "yang-patch-status" message.

   The server will save the running datastore to non-volatile storage if
   it supports non-volatile storage, and if the running datastore
   contents have changed.  This will be done in an implementation-
   specific manner.

   Refer to Appendix D.1.2 for a example of a successful YANG Patch Edit Operations

2.6.
   response.

2.7.  Error Handling

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

   All the specified edits MUST be applied or the target datastore
   contents MUST be returned to its original state before the PATCH
   method started.

   The server will save

   If a YANG Patch is completed with errors, the running datastore server MUST return a
   "200 OK" status-line, and a response message-body containing a
   "yang-patch-status" message.

   Refer to non-volatile storage if
   it has changed, after the edits have been successfully completed.

2.7. Appendix D.1.1 for a example of an error YANG Patch
   response.

2.8.  yang-patch RESTCONF Capability

   A URI is defined to identify the YANG Patch extension to the base
   RESTCONF protocol.  If the server supports the YANG Patch media type,
   then the "yang-patch" RESTCONF capability defined in Section 4.4 MUST
   be present in the "capability" leaf-list in the
   "ietf-restconf-monitoring" module defined in
   [I-D.ietf-netconf-restconf].

3.  YANG Module
   The "ietf-yang-patch" module defines conceptual definitions with the
   'restconf-media-type' extension statements, which are not meant to be
   implemented as datastore contents by a server.

   The "ietf-restconf" module from [I-D.ietf-netconf-restconf] is used
   by this module for the 'restconf-media-type' extension definition.

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

   <CODE BEGINS> file "ietf-yang-patch@2015-04-30.yang" "ietf-yang-patch@2016-03-16.yang"

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

     import ietf-yang-types { prefix yang; }

     import ietf-restconf {
       prefix rc;
       revision-date 2015-10-18; 2016-03-16;
     }

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

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

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

        WG Chair: Mahesh Jethanandani
                  <mailto:mjethanandani@gmail.com>

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

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

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

     description
       "This module contains conceptual YANG specifications
        for the YANG Patch and YANG Patch Status data structures.

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

        Copyright (c) 2015 2016 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Simplified BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

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

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

     // RFC Ed.: remove this note
     // Note: extracted from draft-ietf-netconf-yang-patch-07.txt draft-ietf-netconf-yang-patch-08.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2015-12-15 2016-03-16 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: YANG Patch Media Type.";
     }

     typedef target-resource-offset {
       type yang:xpath1.0;
       description
         "Contains an XPath absolute path expression identifying
          a sub-resource within the target resource.
          The document root for this XPath expression is the
          target resource that is specified in the
          protocol operation (e.g., the URI for the PATCH request).";
     }

     rc:restconf-media-type "application/yang.patch" {
       uses yang-patch;
     }
     rc:restconf-media-type "application/yang.patch-status" {
       uses yang-patch-status;
     }

     grouping yang-patch {

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

       container yang-patch {
         description
           "Represents a conceptual sequence of datastore edits,
            called a patch. Each patch is given a client-assigned
            patch identifier. Each edit MUST be applied
            in ascending order, and all edits MUST be applied.
            If any errors occur, then the target datastore MUST NOT
            be changed by the patch operation.

            YANG datastore validation (defined in RFC 6020, section
            8.3.3) is performed before any edits
            have been applied to the running datastore.

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

         reference
           "RFC 6020,
           "draft-ietf-netmod-rfc6020bis, section 8.3.";

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

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

         }

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

           description
             "Represents one edit within the YANG Patch
              request message.  The edit list is applied
              in the following manner:

                - The first edit is conceptually applied to a copy
                  of the existing target datastore, e.g., the
                  running configuration datastore.
                - Each ascending edit is conceptually applied to
                  the result of the previous edit(s).
                - After all edits have been successfully processed,
                  the result is validated according to YANG constraints.
                - If successful, the server will attempt to apply
                  the result to the target datastore. ";

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

           leaf operation {
             type enumeration {
               enum create {
                 description
                   "The target data node is created using the
                    supplied value, only if it does not already
                    exist.";
                    exist.get' leaf identifies the data node to be
                    created, not the parent data node.";
               }
               enum delete {
                 description
                   "Delete the target node, only if the data resource
                    currently exists, otherwise return an error.";
               }
               enum insert {
                 description
                   "Insert the supplied value into a user-ordered
                    list or leaf-list entry. The target node must
                    represent a new data resource. If the 'where'
                    parameter is set to 'before' or 'after', then
                    the 'point' parameter identifies the insertion
                    point for the target node.";
               }
               enum merge {
                 description
                   "The supplied value is merged with the target data
                    node.";
               }
               enum move {
                 description
                   "Move the target node. Reorder a user-ordered
                    list or leaf-list. The target node must represent
                    an existing data resource. If the 'where' parameter
                    is set to 'before' or 'after', then the 'point'
                    parameter identifies the insertion point to move
                    the target node.";
               }
               enum replace {
                 description
                   "The supplied value is used to replace the target
                    data node.";
               }
               enum remove {
                 description
                   "Delete the target node if it currently exists.";
               }
             }
             mandatory true;
             description
               "The datastore operation requested for the associated
                edit entry";
           }

           leaf target {
             type target-resource-offset;
             mandatory true;
             description
               "Identifies the target data resource node for the edit
                operation.";
                operation. If the target has the value '/', then
                the target data node is the target resource.
                The target node MUST identify a data resource,
                not the datastore resource.";
           }

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

           leaf where {
             when "../operation = 'insert' or ../operation = 'move'" {
               description
                 "Where leaf only applies for insert or move
                  operations.";
             }
             type enumeration {
               enum before {
                 description
                   "Insert or move a data node before the data resource
                    identified by the 'point' parameter.";
               }
               enum after {
                 description
                   "Insert or move a data node after the data resource
                    identified by the 'point' parameter.";
               }
               enum first {
                 description
                   "Insert or move a data node so it becomes ordered
                    as the first entry.";
               }
               enum last {
                 description
                   "Insert or move a data node so it becomes ordered
                    as the last entry.";
               }
             }
             default last;
             description
               "Identifies where a data resource will be inserted or
                moved. YANG only allows these operations for
                list and leaf-list data nodes that are ordered-by
                user.";
           }
           anydata value {
             when "../operation = 'create' "
                + "or ../operation = 'merge' "
                + "or ../operation = 'replace' "
                + "or ../operation = 'insert'" {
               description
                 "Value node only used for create, merge,
                  replace, and insert operations";
             }
             description
               "Value used for this edit operation.  The anydata 'value'
                contains the target resource associated with the
                'target' leaf.

                For example, suppose the target node is a YANG container
                named foo:

                    container foo {
                      leaf a { type string; }
                      leaf b { type int32; }
                    }

                The 'value' node will contain contains one instance of foo:

                    <value>
                       <foo xmlns='example-foo-namespace'>
                          <a>some value</a>
                          <b>42</b>
                       </foo>
                    </value>
                 ";
           }
         }
       }

     } // grouping yang-patch

     grouping yang-patch-status {

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

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

         leaf patch-id {
           type string;
           description
             "The patch-id value used in the request"; request.
              If there was no patch-id present in the request
              then this field will not be present.";
         }

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

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

         container edit-status {
           description
             "This container will be present if there are
              edit-specific status responses to report.
              If all edits succeeded and the 'global-status'
              returned  is 'ok', then a server MAY omit this
              container";

           list edit {
             key edit-id;

             description
               "Represents a list of status responses,
                corresponding to edits in the YANG Patch
                request message.  If an edit entry was
                skipped or not reached by the server,
                then this list will not contain a corresponding
                entry for that edit.";

             leaf edit-id {
               type string;
                description
                  "Response status is for the edit list entry
                   with this edit-id value.";
             }
             choice edit-status-choice {
               description
                 "A choice between different types of status
                  responses for each edit entry.";
               leaf ok {
                 type empty;
                 description
                   "This edit entry was invoked without any
                    errors detected by the server associated
                    with this edit.";
               }
               case errors {
                 uses rc:errors;
                 description
                   "The server detected errors associated with the
                     edit identified by the same edit-id value.";
               }
             }
           }
         }
       }
     }  // grouping yang-patch-status

   }

   <CODE ENDS>

4.  IANA Considerations

4.1.  YANG Module Registry

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

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

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

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

4.2.  application/yang.patch Media Types

   The MIME media type for a YANG Patch document is application/
   yang.patch.

      Type name: application

      Subtype name: yang.patch

      Required parameters: none

      Optional parameters: none

      Encoding considerations: 8-bit

      Security considerations: See Section 5 of RFC XXXX

      Interoperability considerations: none

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

4.3.  application/yang.patch-status Media Types

   The MIME media type for a YANG Patch status document is application/
   yang.patch-status.

      Type name: application

      Subtype name: yang.patch-status

      Required parameters: none

      Optional parameters: none

      Encoding considerations: 8-bit

      Security considerations: See Section 5 of RFC XXXX
      Interoperability considerations: none

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

4.4.  RESTCONF Capability URNs

   This document registers one capability identifier in "RESTCONF
   Protocol Capability URNs" registry

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

     :yang-patch
         urn:ietf:params:restconf:capability:yang-patch:1.0

5.  Security Considerations

   The YANG Patch media type does not introduce any significant new
   security threats, beyond what is described in
   [I-D.ietf-netconf-restconf].  This document defines edit processing
   instructions for a variant of the PATCH method, as used within the
   RESTCONF protocol.

   It may be possible to use YANG Patch with other protocols besides
   RESTCONF, which is outside the scope of this document.

   It is important for server implementations to carefully validate all
   the edit request parameters in some manner.  If the entire YANG Patch
   request cannot be completed, then no configuration changes to the
   system are done.

   A server implementation SHOULD attempt to prevent system disruption
   due to partial processing of the YANG Patch edit list.  It may be
   possible to construct an attack on such a server, which relies on the
   edit processing order mandated by YANG Patch.

6.  Normative References

   [I-D.ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", draft-ietf-netconf-restconf-08 (work in
              progress), October 2015.

   [I-D.ietf-netmod-rfc6020bis]
              Bjorklund, M., "The YANG 1.1 Data Modeling Language",
              draft-ietf-netmod-rfc6020bis-11 (work in progress),
              February 2016.

   [I-D.ietf-netmod-yang-json]
              Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              draft-ietf-netmod-yang-json-06 (work in progress), October
              2015.

   [I-D.ietf-netmod-yang-metadata]
              Lhotka, L., "Defining and Using Metadata with YANG",
              draft-ietf-netmod-yang-metadata-02 (work in progress),
              September 2015.

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

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

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

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

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

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

   [RFC7158]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7158, March 2013.

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

Appendix A.  Acknowledgements
   The authors would like to thank the following people for their
   contributions to this document: Rex Fernando.

   Contributions to this material by Andy Bierman are based upon work
   supported by the The 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).

Appendix B.  Change Log

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

   The YANG Patch issue tracker can be found here: https://github.com/
   netconf-wg/yang-patch/issues

B.1.  v07 to v08

   o  clarified target datastore and target data node terms

   o  clarified that target leaf can be single forward slash '/'

   o  added Successful edit response handling section

   o  clarified that YANG Patch draft is for RESTCONF protocol only but
      may be defined for other protocols outside this document

   o  clarified that YANG Patch draft is for configuration datastores
      only but may be defined for other datastore types outside this
      document

   o  fixed typos

B.2.  v06 to v07

   o  converted YANG module to YANG 1.1

   o  changed anyxml value to anydata value

   o  updated import revision date for ietf-restconf

   o  updated revision date for ietf-yang-patch because import-by-
      revision date needed to be changed

B.2.

B.3.  v05 to v06
   o  changed errors example so a full request and error response is
      shown in XML format

   o  fixed error-path to match instance-identifier encoding for both
      XML and JSON

   o  added references for YANG to JSON and YANG Metadata drafts

   o  clarified that YANG JSON drafts are used for encoding, not plain
      JSON

B.3.

B.4.  v04 to v05

   o  updated reference to RESTCONF

B.4.

B.5.  v03 to v04

   o  removed NETCONF specific text

   o  changed data-resource-offset typedef from a relative URI to an
      XPath absolute path expression

   o  clarified insert operation

   o  removed requirement that edits MUST be applied in ascending order

   o  change SHOULD keep datastore unchanged on error to MUST (this is
      required by HTTP PATCH)

   o  removed length restriction on 'comment' leaf

   o  updated YANG tree for example-jukebox library

B.5.

B.6.  v02 to v03

   o  added usage of restconf-media-type extension to map the yang-patch
      and yang-patch-status groupings to media types

   o  added yang-patch RESTCONF capability URI

   o  Added sub-section for terms used from RESTCONF

   o  filled in security considerations section

B.6.

B.7.  v01 to v02

   o  Reversed order of change log
   o  Clarified anyxml structure of "value" parameter within a YANG
      patch request (github issue #1)

   o  Updated RESTCONF reference

   o  Added note to open issues section to check github instead

B.7.

B.8.  v00 to v01

   o  Added text requiring support for Accept-Patch header, and removed
      'Identification of YANG Patch capabilities' open issue.

   o  Removed 'location' leaf from yang-patch-status grouping

   o  Removed open issue 'Protocol independence' because the location
      leaf was removed.

   o  Removed open issue 'RESTCONF coupling' because there is no concern
      about a normative reference to RESTCONF.  There may need to be a
      YANG 1.1 mechanism to allow protocol template usage (instead of
      grouping wrapper).

   o  Removed open issue 'Is the delete operation needed'.  It was
      decided that both delete and remove should remain as operations
      and clients can choose which one to use.  This is not an
      implementation burden on the server.

   o  Removed open issue 'global-errors needed'.  It was decided that
      they are needed as defined because the global <ok/> is needed and
      the special key value for edit=global error only allows for 1
      global error.

   o  Removed open issue 'Is location leaf needed'.  It was decided that
      it is not needed so this leaf has been removed.

   o  Removed open issue 'Bulk editing support in yang-patch-status'.
      The 'location' leaf has been removed so this issue is no longer
      applicable.

   o  Removed open issue 'Edit list mechanism'.  Added text to the
      'edit' list description-stmt about how the individual edits must
      be processed.  There is no concern about duplicate edits which
      cause intermediate results to be altered by subsequent edits in
      the same edit list.

B.8.

B.9.  bierman:yang-patch-00 to ietf:yang-patch-00

   o  Created open issues section

Appendix C.  Open Issues

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

   Refer to the github issue tracker for any open issues:

   https://github.com/netconf-wg/yang-patch/issues [1]

Appendix D.  Example YANG Module

   The example YANG module used in this document represents a simple
   media jukebox interface.  The "example-jukebox" YANG module is
   defined in [I-D.ietf-netconf-restconf].

   YANG Tree Diagram for "example-jukebox" Module:

   +--rw jukebox!
      +--rw library
      |  +--rw artist* [name]
      |  |  +--rw name     string
      |  |  +--rw album* [name]
      |  |     +--rw name     string
      |  |     +--rw genre?   identityref
      |  |     +--rw year?    uint16
      |  |     +--rw admin
      |  |     |  +--rw label?              string
      |  |     |  +--rw catalogue-number?   string
      |  |     +--rw song* [name]
      |  |        +--rw name        string
      |  |        +--rw location    string
      |  |        +--rw format?     string
      |  |        +--rw length?     uint32
      |  +--ro artist-count?   uint32
      |  +--ro album-count?    uint32
      |  +--ro song-count?     uint32
      +--rw playlist* [name]
      |  +--rw name           string
      |  +--rw description?   string
      |  +--rw song* [index]
      |     +--rw index    uint32
      |     +--rw id       leafref
      +--rw player
         +--rw gap?   decimal64

   rpcs:

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

D.1.  YANG Patch Examples

   This section includes RESTCONF examples.  Most examples are shown in
   JSON encoding [RFC7158], and some are shown in XML encoding
   [W3C.REC-xml-20081126].

D.1.1.  Add Resources: Error

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

    Request from client:

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

   <yang-patch xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch">
     <patch-id>add-songs-patch</patch-id>
     <edit>
       <edit-id>edit1</edit-id>
       <operation>create</operation>
       <target>/song</target>
       <value>
         <song xmlns="http://example.com/ns/example-jukebox">
           <name>Bridge Burning</name>
           <location>/media/bridge_burning.mp3</location>
           <format>MP3</format>
           <length>288</length>
         </song>
       </value>
     </edit>
     <edit>
       <edit-id>edit2</edit-id>
       <operation>create</operation>
       <target>/song</target>
       <value>
         <song xmlns="http://example.com/ns/example-jukebox">
           <name>Rope</name>
           <location>/media/rope.mp3</location>
           <format>MP3</format>
           <length>259</length>
         </song>
       </value>
     </edit>
     <edit>
       <edit-id>edit3</edit-id>
       <operation>create</operation>
       <target>/song</target>
       <value>
         <song xmlns="http://example.com/ns/example-jukebox">
           <name>Dear Rosemary</name>
           <location>/media/dear_rosemary.mp3</location>
           <format>MP3</format>
           <length>269</length>
         </song>
       </value>
     </edit>
   </yang-patch>

    XML Response from server:

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

    <yang-patch-status
       xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-patch">
      <patch-id>add-songs-patch</patch-id>
      <edit-status>
        <edit>
           <edit-id>edit1</edit-id>
           <errors>
              <error>
                 <error-type>application</error-type>
                 <error-tag>data-exists</error-tag>
                 <error-path
                   xmlns:jb="http://example.com/ns/example-jukebox">
                   /jb:jukebox/jb:library
                   /jb:artist[jb:name='Foo Fighters']
                   /jb:album[jb:name='Wasting Light']
                   /jb:song[jb:name='Burning Light']
                 </error-path>
                 <error-message>
                   Data already exists, cannot be created
                 </error-message>

              </error>
           </errors>
        </edit>
     </edit-status>
   </yang-patch-status>

    JSON Response from server:

    The following response is shown in JSON format to highlight the
    difference in the "error-path" object encoding. For JSON, the
    instance-identifier encoding in the "JSON Encoding of YANG
    Data" draft is used. The "error-path" string is wrapped for
    display purposes.

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

      {
        "ietf-yang-patch:yang-patch-status" : {
          "patch-id" : "add-songs-patch",
          "edit-status" : {
            "edit" : [
              {
                "edit-id" : "edit1",
                "errors" : {
                  "error" : [
                    {
                      "error-type": "application",
                      "error-tag": "data-exists",
                      "error-path": "/example-jukebox:jukebox/library
                         /artist[name='Foo Fighters']
                         /album[name='Wasting Light']
                         /song[name='Burning Light']",
                      "error-message":
                        "Data already exists, cannot be created"
                    }
                  ]
                }
              }
            ]
          }
        }
      }

D.1.2.  Add Resources: Success

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

   o  Each of 2 edits contains one song.

   o  Both edits succeed and new sub-resources are created

    Request from client:

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

      {
        "ietf-yang-patch:yang-patch" : {
          "patch-id" : "add-songs-patch-2",
          "edit" : [
            {
              "edit-id" : "edit1",
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Rope",
                  "location" : "/media/rope.mp3",
                  "format" : "MP3",
                  "length" : 259
                }
              }
            },
            {
              "edit-id" : "edit2",
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Dear Rosemary",
                  "location" : "/media/dear_rosemary.mp3",
                  "format" : "MP3",
                  "length" : 269
                }
              }
            }

          ]
        }
      }

    Response from server:

      HTTP/1.1 200 Success
      Date: Mon, 23 Apr 2012 13:01:20 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 13:01:20 GMT
      Content-Type: application/yang.patch-status+json

      {
        "ietf-yang-patch:yang-patch-status" : {
          "patch-id" : "add-songs-patch-2",
          "ok" : [null]
        }
      }

D.1.3.  Move list entry example

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

    Request from client:

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

      {
        "ietf-yang-patch:yang-patch" : {
          "patch-id" : "move-song-patch",
          "comment" : "Move song 1 after song 3",
          "edit" : [
            {
              "edit-id" : "edit1",
              "operation" : "move",
              "target" : "/song/1",
              "point" : "/song3",
              "where" : "after"
            }
          ]
        }

      }

    Response from server:

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

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

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