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YANG Patch Media Type
draft-ietf-netconf-yang-patch-00

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8072.
Authors Andy Bierman , Martin Björklund , Kent Watsen , Rex Fernando
Last updated 2014-03-23
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draft-ietf-netconf-yang-patch-00
Network Working Group                                         A. Bierman
Internet-Draft                                                 YumaWorks
Intended status: Standards Track                            M. Bjorklund
Expires: September 23, 2014                               Tail-f Systems
                                                               K. Watsen
                                                        Juniper Networks
                                                             R. Fernando
                                                                   Cisco
                                                          March 22, 2014

                         YANG Patch Media Type
                    draft-ietf-netconf-yang-patch-00

Abstract

   This document describes a method for applying patches to NETCONF
   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 September 23, 2014.

Copyright Notice

   Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
       1.1.1.  NETCONF  . . . . . . . . . . . . . . . . . . . . . . .  3
       1.1.2.  HTTP . . . . . . . . . . . . . . . . . . . . . . . . .  4
       1.1.3.  YANG . . . . . . . . . . . . . . . . . . . . . . . . .  4
       1.1.4.  Terms  . . . . . . . . . . . . . . . . . . . . . . . .  5
       1.1.5.  Tree Diagrams  . . . . . . . . . . . . . . . . . . . .  5
   2.  YANG Patch . . . . . . . . . . . . . . . . . . . . . . . . . .  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
     2.5.  Edit Operations  . . . . . . . . . . . . . . . . . . . . .  7
     2.6.  Error Handling . . . . . . . . . . . . . . . . . . . . . .  8
   3.  YANG Module  . . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
     4.1.  YANG Module Registry . . . . . . . . . . . . . . . . . . . 18
     4.2.  application/yang.patch Media Types . . . . . . . . . . . . 18
     4.3.  application/yang.patch-status Media Types  . . . . . . . . 18
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   6.  Normative References . . . . . . . . . . . . . . . . . . . . . 21
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . . 22
     A.1.  bierman:yang-patch-00 to ietf:yang-patch-00  . . . . . . . 22
   Appendix B.  Open Issues . . . . . . . . . . . . . . . . . . . . . 23
     B.1.  Identification of YANG Patch capabilities  . . . . . . . . 23
     B.2.  Protocol independence  . . . . . . . . . . . . . . . . . . 23
     B.3.  RESTCONF coupling  . . . . . . . . . . . . . . . . . . . . 23
     B.4.  Delete operation needed? . . . . . . . . . . . . . . . . . 24
     B.5.  global-errors needed?  . . . . . . . . . . . . . . . . . . 24
     B.6.  Is location leaf needed? . . . . . . . . . . . . . . . . . 24
     B.7.  Bulk editing support in yang-patch-status  . . . . . . . . 24
     B.8.  Edit list mechanism  . . . . . . . . . . . . . . . . . . . 24
   Appendix C.  Example YANG Module . . . . . . . . . . . . . . . . . 26
     C.1.  YANG Patch Examples  . . . . . . . . . . . . . . . . . . . 26
       C.1.1.  Patch an Existing Data Resource  . . . . . . . . . . . 27
       C.1.2.  Add Resources: Error . . . . . . . . . . . . . . . . . 27
       C.1.3.  Add Resources: Success . . . . . . . . . . . . . . . . 29
       C.1.4.  Move list entry example  . . . . . . . . . . . . . . . 31
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33

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1.  Introduction

   There is a need for standard mechanisms to patch NETCONF [RFC6241]
   datastores which contain conceptual data that conforms to schema
   specified with YANG [RFC6020].  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 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] or custom
   NETCONF operations (defined with the YANG rpc-stmt).

   YANG Patch is designed to support multiple protocols with the same
   mechanisms.  The RESTCONF [RESTCONF] protocol utilizes YANG Patch
   with the HTTP PATCH method.  A new RPC operation can be defined to
   utilize YANG Patch in the NETCONF protocol.  Both the RESTCONF and
   NETCONF protocols are designed to utilize the YANG data modeling
   language to specify content schema modules.

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  candidate configuration datastore

   o  client

   o  configuration data

   o  datastore

   o  configuration datastore

   o  protocol operation

   o  running configuration datastore

   o  server

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   o  startup configuration datastore

   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]:

   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)

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   o  non-presence container (or NP-container)

   o  ordered-by system

   o  ordered-by user

1.1.4.  Terms

   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".

1.1.5.  Tree Diagrams

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

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

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

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

   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.

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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 with
   the 'yang-patch' container definition in the YANG module 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.

   For NETCONF, a YANG "rpc" statement must be defined.  The
   "yang-patch" grouping MUST be included in the input parameters and
   the "yang-patch-status" grouping MUST be included in the output
   parameters.

2.1.  Target Resource

   The YANG Patch operation uses a conceptual root within a NETCONF
   configuration datastore to identity the patch point for the edit
   operation.  This root can be the datastore itself, or 1 or more data
   nodes within the datastore.

   For RESTCONF, the target resource is derived from the request URI.

   For NETCONF, the target resource MUST be defined as an input
   parameter in the YANG "rpc" statement.

2.2.  yang-patch Input

   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

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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.

   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
                  +--:(location)
                  |  +--rw location?   inet:uri
                  +--:(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 an
   absolute path expression.  The first node specified in the "target"
   leaf is a top-level data node defined within a YANG module.

   If the target resource specified in the request URI identifies a data
   resource, then the path string in the "target" leaf is a relative
   path expression.  The first node specified in the "target" leaf is a
   child node of the data node associated with the target resource.

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

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   operations, but also includes some new operations.

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

                        YANG Patch Edit Operations

2.6.  Error Handling

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

   All the specified edits MUST be applied or the target datastore
   contents SHOULD be returned to its original state before the PATCH
   method started.  The server MAY fail to restore the contents of the
   target datastore completely and with certainty.  It is possible for a
   rollback to fail or an "undo" operation to fail.

   The server will save the running datastore to non-volatile storage if
   it has changed, after the edits have been attempted.

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3.  YANG Module

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

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

   The "ietf-restconf" module from [RESTCONF] is used by this module for
   a grouping definition.

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

   <CODE BEGINS> file "ietf-yang-patch@2014-03-22.yang"

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

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

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

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

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

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

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

        Editor:   Rex Fernando
                  <mailto:rex@cisco.com>";

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     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) 2014 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

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

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

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

     // RFC Ed.: remove this note
     // Note: extracted from draft-ietf-netconf-yang-patch-00.txt

     // RFC Ed.: update the date below with the date of RFC publication
     // and remove this note.
     revision 2014-03-22 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: YANG Patch";
     }

     typedef target-resource-offset {
       type string {
         length "1 .. max";
       }
       description
         "Contains a relative Data Resource Identifier formatted string
          to identify a specific data sub-resource instance.
          The document root for all data resources is a
          target data resource that is specified in the
          object definition using this data type.";
     }

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     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.

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

            YANG datastore validation (defined in RFC 6020, section
            8.3.3) is performed after all edits have been
            individually validated.

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

         reference
           "RFC 6020, section 8.3.";

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

         leaf comment {
           type string {
             length "0 .. 1024";
           }
           description
             "An arbitrary string provided by the client to describe

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              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.";

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

           leaf operation {
             type enumeration {
               enum create {
                 description
                   "The target data node is created using the
                    supplied value, only if it does not already
                    exist.";
               }
               enum delete {
                 description
                   "Delete the target node, only if the data resource
                    currently exists, otherwise return an error.";
               }
               enum insert {
                 description
                   "Insert the supplied value into a user-ordered
                    list or leaf-list entry. The target node must
                    represent a new data resource.";
               }
               enum merge {
                 description
                   "The supplied value is merged with the target data
                    node.";
               }
               enum move {
                 description

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                   "Move the target node. Reorder a user-ordered
                    list or leaf-list. The target node must represent
                    an existing data resource.";
               }
               enum replace {
                 description
                   "The supplied value is used to replace the target
                    data node.";
               }
               enum remove {
                 description
                   "Delete the target node if it currently exists.";
               }
             }
             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 for the edit
                operation.";
           }

           leaf point {
             when "(../operation = 'insert' or " +
               "../operation = 'move') and " +
               "(../where = 'before' or ../where = 'after')" {
               description
                 "Point leaf only applies for insert or move
                  operations, before or after an existing entry.";
             }
             type 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.";

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             }
             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.";
           }

           anyxml value {
             when "(../operation = 'create' or " +
               "../operation = 'merge' " +
               "or ../operation = 'replace' or " +
               "../operation = 'insert')" {
               description
                 "Value node only used for create, merge,
                  replace, and insert operations";
             }
             description
               "Value used for this edit operation.";
           }
         }
       }

     } // grouping yang-patch

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     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";
         }

         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.";

           list edit {
             key edit-id;

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             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.";
               }
               leaf location {
                 type inet:uri;
                 description
                   "Contains the Location header value that would be
                    returned if this edit causes a new resource to be
                    created. If the edit identified by the same edit-id
                    value was successfully invoked and a new resource
                    was created, then this field will be returned
                    instead of 'ok'.";
               }
               case errors {
                 uses rc:errors;
                 description
                   "The server detected errors associated with the
                     edit identified by the same edit-id value.";
               }
             }
           }
         }
       }
     }  // grouping yang-patch-status

   }

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   <CODE ENDS>

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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 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: TBD

      Optional parameters: TBD

      Encoding considerations: TBD

      Security considerations: TBD

      Interoperability considerations: TBD

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

4.3.  application/yang.patch-status Media Types

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

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      Type name: application

      Subtype name: yang.patch-status

      Required parameters: TBD

      Optional parameters: TBD

      Encoding considerations: TBD

      Security considerations: TBD

      Interoperability considerations: TBD

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

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5.  Security Considerations

   TBD

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6.  Normative References

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

   [RESTCONF]
              Bierman, A., Bjorklund, M., Watsen, K., and R. Fernando,
              "RESTCONF Protocol", draft-ietf-netconf-restconf-00 (work
              in progress), December 2013.

   [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.

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

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

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Appendix A.  Change Log

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

A.1.  bierman:yang-patch-00 to ietf:yang-patch-00

   o  Created open issues section

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Appendix B.  Open Issues

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

B.1.  Identification of YANG Patch capabilities

   How does a client know that the YANG Patch media type is supported?

   Status: closed-update-pending

   Resolution: the Accept-Patch header defined in RFC 5789 needs to be
   implemented by the server to advertise the media types supported for
   PATCH.

B.2.  Protocol independence

   o  yang-patch/target and point leafs are type target-resource-offset.
      Is this syntax for a relative resource identifier acceptable for
      all protocols?  Acceptable for just NETCONF and RESTCONF?

   o  yang-patch-status/location leaf (type inet:uri) Can this be
      ignored in a protocol such as NETCONF?

   Status: open (pending location issue)

   Solution proposal: Change the 'location' leaf to match the
   'error-node' choice in RESTCONF:

     choice resource-identifier {
       leaf location-path {
         type instance-identifier;
       }
       leaf location-urlpath {
         type rc:data-resource-identifier;
       }
     }

B.3.  RESTCONF coupling

   o  RESTCONF is a normative reference for YANG Patch, imported in YANG
      module for rc:errors grouping.  Is this a problem for protocol
      independence?

   Status: open

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B.4.  Delete operation needed?

   o  Is the delete operation needed?

   Status: closed-update-pending

   Resolution: The delete operation is not needed.  The remove operation
   is good enough, and the ability to delete only if the target data
   node exists is not needed.  The delete option is dependent on the
   treatment of default leafs and RESTCONF tries to hide the with-
   defaults details.

B.5.  global-errors needed?

   o  There are 2 <errors> sections in yang-patch-status (global-errors/
      errors and edit-status/edit/errors).  If a special 'edit-id' value
      was reserved, such as an empty string, it could be used in the
      'edit' list to identify global errors

   Status: open

B.6.  Is location leaf needed?

   The location leaf in each edit is used to identify the sub-resource
   created by the edit request.  Is this leaf needed at all?  The POST
   method needs to return a Location header but no such requirement
   exists for sub-resources created via PATCH.

   Status: open

   Solution proposal: remove location leaf from yang-patch-status.

B.7.  Bulk editing support in yang-patch-status

   What if the protocol is using a bulk edit (such as NETCONF-EX
   <edit2>) and the edit list is applied to multiple nodes?  Should
   'leaf location' be changed to 'leaf-list location'?

   Status: open (pending location issue)

   Solution Proposal: the location leaf will be changed to a leaf-list
   in case multiple sub-resources are created in one edit operation.

B.8.  Edit list mechanism

   o  Is the edit list approach better or worse than the 'config'
      subtree approach used in the <edit-config> operation?  NETCONF
      does not have any constraints on how operation attributes are

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      nested, or whether duplicate nodes are allowed.  There is no
      specified processing order in NETCONF.

   Status: open

   o  Are constraints needed (for either approach) in order to improve
      processing consistency and interoperability?  E.g., no nested
      operations allowed, no duplicates allowed?

   Status: open

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Appendix C.  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 [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 song [name]
         |  |        +--rw name        string
         |  |        +--rw location    string
         |  |        +--rw format?     string
         |  |        +--rw length?     uint32
         |  +--ro artist-count?   uint32
         |  +--ro album-count?    uint32
         |  +--rw song-count?     uint32
         +--rw playlist [name]
         |  +--rw name           string
         |  +--rw description?   string
         |  +--rw song [index]
         |     +--rw index    uint32
         |     +--rw id       instance-identifier
         +--rw player
            +--rw gap?   decimal64

     rpcs:

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

C.1.  YANG Patch Examples

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

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C.1.1.  Patch an Existing Data Resource

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

      PATCH /restconf/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+json

      { "example-jukebox:year" : 2011 }

   If the field is updated, the server might respond:

      HTTP/1.1 204 No Content
      Date: Mon, 23 Apr 2012 17:49:30 GMT
      Server: example-server
      Last-Modified: Mon, 23 Apr 2012 17:49:30 GMT
      ETag: b2788923da4c

   The XML encoding for the same request might be:

      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

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

C.1.2.  Add Resources: Error

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

    Request from client:

      PATCH /restconf/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

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      {
        "ietf-restconf:yang-patch" : {
          "patch-id" : "add-songs-patch",
          "edit" : [
            {
              "edit-id" : 1,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Bridge Burning",
                  "location" : "/media/bridge_burning.mp3",
                  "format" : "MP3",
                  "length" : 288
                }
              }
            },
            {
              "edit-id" : 2,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Rope",
                  "location" : "/media/rope.mp3",
                  "format" : "MP3",
                  "length" : 259
                }
              }
            },
            {
              "edit-id" : 3,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Dear Rosemary",
                  "location" : "/media/dear_rosemary.mp3",
                  "format" : "MP3",
                  "length" : 269
                }
              }
            }
          ]
        }
      }

    Response from server:

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

      {
        "ietf-restconf:yang-patch-status" : {
          "patch-id" : "add-songs-patch",
          "edit-status" : {
            "edit" : [
              {
                "edit-id" : 1,
                "errors" : {
                  "error" : [
                    {
                      "error-type": "application",
                      "error-tag": "data-exists",
                      "error-path": "/example-jukebox:jukebox/library
                         /artist/Foo%20Fighters/album/Wasting%20Light
                         /song/Burning%20Light",
                      "error-message":
                        "Data already exists, cannot be created"
                    }
                  ]
                }
              }
            ]
          }
        }
      }

C.1.3.  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

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      Accept: application/yang.patch-status+json
      Content-Type: application/yang.patch+json

      {
        "ietf-restconf:yang-patch" : {
          "patch-id" : "add-songs-patch-2",
          "edit" : [
            {
              "edit-id" : 1,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Rope",
                  "location" : "/media/rope.mp3",
                  "format" : "MP3",
                  "length" : 259
                }
              }
            },
            {
              "edit-id" : 2,
              "operation" : "create",
              "target" : "/song",
              "value" : {
                "song" : {
                  "name" : "Dear Rosemary",
                  "location" : "/media/dear_rosemary.mp3",
                  "format" : "MP3",
                  "length" : 269
                }
              }
            }
          ]
        }
      }

    Response from server:

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

      {
        "ietf-restconf:yang-patch-status" : {
          "patch-id" : "add-songs-patch-2",

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          "ok" : [null],
          "edit-status" : {
            "edit" : [
              {
                "edit-id" : 1,
                "location" : "http://example.com/restconf/
                   data/example-jukebox:jukebox/library/artist/
                   Foo%20Fighters/album/Wasting%20Light/song/Rope"
              },
              {
                "edit-id" : 2,
                "location" : "http://example.com/restconf/
                   data/example-jukebox:jukebox/library/artist/
                   Foo%20Fighters/album/Wasting%20Light/song/
                   Dear%20Rosemary"
              }
            ]
          }
        }
      }

C.1.4.  Move list entry example

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

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    Request from client:

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

    Response from server:

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

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

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Authors' Addresses

   Andy Bierman
   YumaWorks

   Email: andy@yumaworks.com

   Martin Bjorklund
   Tail-f Systems

   Email: mbj@tail-f.com

   Kent Watsen
   Juniper Networks

   Email: kwatsen@juniper.net

   Rex Fernando
   Cisco

   Email: rex@cisco.com

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