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IETF RFC 8072
Last modified on Wednesday, February 22nd, 2017
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Internet Engineering Task Force (IETF) A. Bierman
Request for Comments: 8072 YumaWorks
Category: Standards Track M. Bjorklund
ISSN: 2070-1721 Tail-f Systems
K. Watsen
Juniper Networks
February 2017
YANG Patch Media Type
 Abstract
This document describes a method for applying patches to
configuration datastores using data defined with the YANG data
modeling language.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 8072.
Copyright Notice
Copyright (c) 2017 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.
Bierman, et al. Standards Track PAGE 1 
RFC 8072 YANG Patch February 2017
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. RESTCONF ............................................4
1.1.5. YANG Patch ..........................................5
1.1.6. Examples ............................................5
1.1.7. Tree Diagram Notations ..............................6
2. YANG Patch ......................................................6
2.1. Target Resource ............................................7
2.2. yang-patch Request .........................................8
2.3. yang-patch-status Response .................................9
2.4. Target Data Node ..........................................10
2.5. Edit Operations ...........................................11
2.6. Successful Edit Response Handling .........................11
2.7. Error Handling ............................................12
2.8. ":yang-patch" RESTCONF Capability .........................12
3. YANG Module ....................................................13
4. IANA Considerations ............................................22
4.1. Registrations for New URI and YANG Module .................22
4.2. Media Types ...............................................23
4.2.1. Media Type "application/yang-patch+xml" ............23
4.2.2. Media Type "application/yang-patch+json" ...........24
4.3. RESTCONF Capability URNs ..................................25
5. Security Considerations ........................................25
6. References .....................................................26
6.1. Normative References ......................................26
6.2. Informative References ....................................27
Appendix A. Example YANG Module ...................................28
A.1. YANG Patch Examples ........................................29
A.1.1. Add Resources: Error ...................................29
A.1.2. Add Resources: Success .................................33
A.1.3. Insert List Entry ......................................35
A.1.4. Move List Entry ........................................36
A.1.5. Edit Datastore Resource ................................37
Acknowledgements ..................................................39
Authors' Addresses ................................................39
Bierman, et al. Standards Track PAGE 2
RFC 8072 YANG Patch February 2017
1. Introduction
There is a need for standard mechanisms to patch datastores defined
in [RFC 6241], which contain conceptual data that conforms to schema
specified with YANG [RFC 7950]. An "ordered 'edit' list" approach is
needed to provide RESTCONF client developers with more precise
RESTCONF client control of the edit procedure than the "plain patch"
mechanism found in [RFC 8040].
This document defines a media type for a YANG-based editing mechanism
that can be used with the HTTP PATCH method [RFC 5789]. YANG Patch is
designed to support the RESTCONF protocol, defined in [RFC 8040].
This document only specifies the use of the YANG Patch media type
with the RESTCONF protocol.
It may be possible to use YANG Patch with other protocols besides
RESTCONF. This is outside the scope of this document. For any
protocol that supports the YANG Patch media type, if the entire patch
document cannot be successfully applied, then the server MUST NOT
apply any of the changes. 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 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119].
1.1.1. NETCONF
The following terms are defined in [RFC 6241]:
o configuration data
o datastore
o configuration datastore
o protocol operation
o running configuration datastore
o state data
o user
Bierman, et al. Standards Track PAGE 3
RFC 8072 YANG Patch February 2017
1.1.2. HTTP
The following terms are defined in [RFC 7230]:
o header field
o message-body
o query
o request URI
The following terms are defined in [RFC 7231]:
o method
o request
o resource
1.1.3. YANG
The following terms are defined in [RFC 7950]:
o container
o data node
o leaf
o leaf-list
o list
1.1.4. RESTCONF
The following terms are defined in [RFC 8040]:
o application/yang-data+xml
o application/yang-data+json
o data resource
o datastore resource
o patch
Bierman, et al. Standards Track PAGE 4
RFC 8072 YANG Patch February 2017
o RESTCONF capability
o target resource
o YANG data template
1.1.5. YANG Patch
The following terms are used within this document:
o RESTCONF client: a client that implements the RESTCONF protocol.
o RESTCONF server: a server that implements the RESTCONF protocol.
o YANG Patch: a conceptual edit request using the "yang-patch" YANG
Patch template, defined in Section 3. In HTTP, refers to a PATCH
method where a representation uses either the media type
"application/yang-patch+xml" or "application/yang-patch+json".
o YANG Patch Status: a conceptual edit status response using the
YANG "yang-patch-status" YANG data template, defined in Section 3.
In HTTP, refers to a response message for a PATCH method, where it
has a representation with either the media type
"application/yang-data+xml" or "application/yang-data+json".
o YANG Patch template: similar to a YANG data template, except that
it has a representation with the media type
"application/yang-patch+xml" or "application/yang-patch+json".
1.1.6. Examples
Some protocol message lines within examples throughout this document
are split into multiple lines for display purposes only. When a line
ends with a backslash ("\") as the last character, the line is
wrapped for display purposes. It is to be considered to be joined to
the next line by deleting the backslash, the following line break,
and the leading whitespace of the next line.
Bierman, et al. Standards Track PAGE 5
RFC 8072 YANG Patch February 2017
1.1.7. Tree Diagram Notations
A simplified graphical representation of the data model is used in
this document. The meanings of the symbols in these diagrams are as
follows:
o Brackets "[" and "]" enclose list keys.
o Abbreviations before data node names: "rw" means configuration
data (read-write), "ro" means state data (read-only), and "x"
means operation resource (executable).
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 RESTCONF server. The specific fields are
defined in the YANG module in Section 3.
The YANG Patch operation is invoked by the RESTCONF client by
sending a PATCH method request with a representation using either
the media type "application/yang-patch+xml" or
"application/yang-patch+json". This message-body representing the
YANG Patch input parameters MUST be present.
YANG Patch has some features that are not possible with the
"plain-patch" mechanism defined in RESTCONF [RFC 8040]:
o YANG Patch allows multiple sub-resources to be edited within the
same PATCH method.
o YANG Patch allows a more precise edit operation than the
"plain patch" mechanism found in [RFC 8040]. There are seven
operations supported ("create", "delete", "insert", "merge",
"move", "replace", and "remove").
o YANG Patch uses an "edit" list with an explicit processing order.
The edits are processed in client-specified order, and error
processing can be precise even when multiple errors occur in the
same YANG Patch request.
Bierman, et al. Standards Track PAGE 6
RFC 8072 YANG Patch February 2017
The YANG Patch "patch-id" may be useful for debugging and SHOULD be
present in any audit logging records generated by the RESTCONF server
for a patch.
The RESTCONF server MUST return the "Accept-Patch" header field in an
OPTIONS response, as specified in [RFC 5789], which includes the
media type for YANG Patch. This is needed by a client to determine
the message-encoding formats supported by the server (e.g., XML,
JSON, or both). The following is an example of an "Accept-Patch"
header:
Accept-Patch: application/yang-patch+xml,application/yang-patch+json
Note that YANG Patch can only edit data resources. The PATCH method
cannot be used to replace the datastore resource. Although the
"ietf-yang-patch" YANG module is written using YANG version 1.1
[RFC 7950], an implementation of YANG Patch can be used with content
defined in YANG version 1 [RFC 6020] as well.
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" [RFC 7951]. If any metadata
needs to be sent in a JSON message, it is encoded according to
"Defining and Using Metadata with YANG" [RFC 7952].
2.1. Target Resource
The YANG Patch operation uses the RESTCONF target resource URI to
identify the resource that will be patched. This can be the
datastore resource itself, i.e., "{+restconf}/data", to edit
top-level configuration data resources, or it can be a configuration
data resource within the datastore resource, e.g.,
"{+restconf}/data/ietf-interfaces:interfaces", to edit sub-resources
within a top-level configuration data resource.
The target resource MUST identify exactly one resource instance. If
more than one resource instance is identified, then the request
MUST NOT be processed and a "400 Bad Request" error response MUST be
sent by the server. If the target resource does not identify any
existing resource instance, then the request MUST NOT be processed
and a "404 Not Found" error response MUST be sent by the server.
Each edit with a YANG Patch identifies a target data node for the
associated edit. This is described in Section 2.4.
Bierman, et al. Standards Track PAGE 7
RFC 8072 YANG Patch February 2017
2.2. yang-patch Request
A YANG Patch is 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", or
"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.
The "merge", "replace", "create", "delete", and "remove" edit
operations have exactly the same meanings as those defined for the
"operation" attribute described in Section 7.2 of [RFC 6241].
Each edit within a YANG Patch MUST identify exactly one data resource
instance. If an edit represents more than one resource instance,
then the request MUST NOT be processed and a "400 Bad Request" error
response MUST be sent by the server. If the edit does not identify
any existing resource instance and the operation for the edit is not
"create", then the request MUST NOT be processed and a "404 Not
Found" error response MUST be sent by the server. A
"yang-patch-status" response MUST be sent by the server identifying
the edit or edits that are not valid.
YANG Patch does not provide any access to specific datastores. How a
server processes an edit if it is co-located with a Network
Configuration Protocol (NETCONF) server that does provide access to
individual datastores is left up to the implementation. A complete
datastore cannot be replaced in the same manner as that provided by
the <copy-config> operation defined in Section 7.3 of [RFC 6241].
Only the specified nodes in a YANG Patch are affected.
A message-body representing the YANG Patch is sent by the RESTCONF
client to specify the edit operation request. When used with the
HTTP PATCH method, this data is identified by the YANG Patch
media type.
Bierman, et al. Standards Track PAGE 8
RFC 8072 YANG Patch February 2017
YANG tree diagram for "yang-patch" container:
+---- yang-patch
+---- patch-id string
+---- comment? string
+---- edit* [edit-id]
+---- edit-id string
+---- operation enumeration
+---- target target-resource-offset
+---- point? target-resource-offset
+---- where? enumeration
+---- value?
2.3. yang-patch-status Response
A message-body representing the YANG Patch Status is returned to the
RESTCONF 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; the syntax specification is defined in
Section 3.
Bierman, et al. Standards Track PAGE 9
RFC 8072 YANG Patch February 2017
YANG tree diagram for "yang-patch-status" container:
+---- yang-patch-status
+---- patch-id string
+---- (global-status)?
| +--:(global-errors)
| | +---- errors
| | +---- error*
| | +---- error-type enumeration
| | +---- error-tag string
| | +---- error-app-tag? string
| | +---- error-path? instance-identifier
| | +---- error-message? string
| | +---- error-info?
| +--:(ok)
| +---- ok? empty
+---- edit-status
+---- edit* [edit-id]
+---- edit-id string
+---- (edit-status-choice)?
+--:(ok)
| +---- ok? empty
+--:(errors)
+---- errors
+---- error*
+---- error-type enumeration
+---- error-tag string
+---- error-app-tag? string
+---- error-path? instance-identifier
+---- error-message? string
+---- error-info?
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 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.
Bierman, et al. Standards Track PAGE 10
RFC 8072 YANG Patch February 2017
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; if it already exists, return an error |
| | |
| delete | delete a data resource if it already exists; if it |
| | does not exist, return an 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 | reorder the target data resource |
| | |
| replace | replace the target data resource with the edit value |
| | |
| remove | remove a data resource if it already exists |
+-----------+-------------------------------------------------------+
YANG Patch Edit Operations
2.6. Successful Edit Response Handling
If a YANG Patch is completed without errors, the RESTCONF server MUST
return a "yang-patch-status" message with a "global-status" choice
set to "ok".
Refer to Appendix A.1.2 for an example of a successful YANG Patch
response.
Bierman, et al. Standards Track PAGE 11
RFC 8072 YANG Patch February 2017
2.7. Error Handling
If a well-formed, schema-valid YANG Patch message is received, then
the RESTCONF server will process the supplied edits in ascending
order. The following error modes apply to the processing of this
"edit" list:
If a YANG Patch is completed with errors, the RESTCONF server SHOULD
return a "yang-patch-status" message. It is possible (e.g., within a
distributed implementation) that an invalid request will be rejected
before the YANG Patch edits are processed. In this case, the server
MUST send the appropriate HTTP error response instead.
Refer to Appendix A.1.1 for an 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 RESTCONF server supports the YANG Patch
media type, then the ":yang-patch" RESTCONF capability defined in
Section 4.3 MUST be present in the "capability" leaf-list in the
"ietf-restconf-monitoring" module defined in [RFC 8040].
Bierman, et al. Standards Track PAGE 12
RFC 8072 YANG Patch February 2017
3. YANG Module
The "ietf-yang-patch" module defines conceptual definitions with the
"yang-data" extension statements, which are not meant to be
implemented as datastore contents by a RESTCONF server.
The "ietf-restconf" module from [RFC 8040] is used by this module for
the "yang-data" extension definition.
<CODE BEGINS>
file "ietf-yang-patch@2017-02-22.yang"
module ietf-yang-patch {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-patch";
prefix "ypatch";
import ietf-restconf { prefix rc; }
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Andy Bierman
<mailto:andy@yumaworks.com>
Author: Martin Bjorklund
<mailto:mbj@tail-f.com>
Author: Kent Watsen
<mailto:kwatsen@juniper.net>";
description
"This module contains conceptual YANG specifications
for 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) 2017 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Bierman, et al. Standards Track PAGE 13
RFC 8072 YANG Patch February 2017
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 8072; see
the RFC itself for full legal notices.";
revision 2017-02-22 {
description
"Initial revision.";
reference
"RFC 8072: YANG Patch Media Type.";
}
typedef target-resource-offset {
type string;
description
"Contains a data resource identifier string representing
a sub-resource within the target resource.
The document root for this expression is the
target resource that is specified in the
protocol operation (e.g., the URI for the PATCH request).
This string is encoded according to the same rules as those
for a data resource identifier in a RESTCONF request URI.";
reference
"RFC 8040, Section 3.5.3.";
}
rc:yang-data "yang-patch" {
uses yang-patch;
}
rc:yang-data "yang-patch-status" {
uses yang-patch-status;
}
Bierman, et al. Standards Track PAGE 14
RFC 8072 YANG Patch February 2017
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 YANG Patch operation.
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 7950, Section 8.3.";
leaf patch-id {
type string;
mandatory true;
description
"An arbitrary string provided by the client to identify
the entire patch. Error messages returned by the server
that pertain to this patch will be identified by this
'patch-id' value. A client SHOULD attempt to generate
unique 'patch-id' values to distinguish between
transactions from multiple clients in any audit logs
maintained by the server.";
}
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.";
}
Bierman, et al. Standards Track PAGE 15
RFC 8072 YANG Patch February 2017
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 that pertain
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. The
'target' 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.";
}
Bierman, et al. Standards Track PAGE 16
RFC 8072 YANG Patch February 2017
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.";
}
Bierman, et al. Standards Track PAGE 17
RFC 8072 YANG Patch February 2017
leaf target {
type target-resource-offset;
mandatory true;
description
"Identifies the target data node for the edit
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
"This 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
"This 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.";
}
Bierman, et al. Standards Track PAGE 18
RFC 8072 YANG Patch February 2017
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
"The anydata 'value' is 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; }
}
Bierman, et al. Standards Track PAGE 19
RFC 8072 YANG Patch February 2017
The 'value' node 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 a 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;
mandatory true;
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.";
Bierman, et al. Standards Track PAGE 20
RFC 8072 YANG Patch February 2017
case global-errors {
uses rc:errors;
description
"This container will be present if global errors that
are 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.";
}
Bierman, et al. Standards Track PAGE 21
RFC 8072 YANG Patch February 2017
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. Registrations for New URI and YANG Module
This document registers one URI as a namespace in the "IETF XML
Registry" [RFC 3688]. It follows the format in RFC 3688.
URI: urn:ietf:params:xml:ns:yang:ietf-yang-patch
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document registers one YANG module in the "YANG Module Names"
registry [RFC 6020].
name: ietf-yang-patch
namespace: urn:ietf:params:xml:ns:yang:ietf-yang-patch
prefix: ypatch
reference: RFC 8072
Bierman, et al. Standards Track PAGE 22
RFC 8072 YANG Patch February 2017
4.2. Media Types
4.2.1. Media Type "application/yang-patch+xml"
Type name: application
Subtype name: yang-patch+xml
Required parameters: None
Optional parameters: None
Encoding considerations: 8-bit
The "utf-8" charset is always used for this type.
Each conceptual YANG data node is encoded according to the
XML Encoding Rules and Canonical Format for the specific
YANG data node type defined in [RFC 7950].
In addition, the "yang-patch" YANG Patch template found
in RFC 8072 defines the structure of a YANG Patch request.
Security considerations: Security considerations related
to the generation and consumption of RESTCONF messages
are discussed in Section 5 of RFC 8072.
Additional security considerations are specific to the
semantics of particular YANG data models. Each YANG module
is expected to specify security considerations for the
YANG data defined in that module.
Interoperability considerations: RFC 8072 specifies the format
of conforming messages and the interpretation thereof.
Published specification: RFC 8072
Applications that use this media type: Instance document
data parsers used within a protocol or automation tool
that utilize the YANG Patch data structure.
Fragment identifier considerations: The syntax and semantics
of fragment identifiers are the same as the syntax and semantics
specified for the "application/xml" media type.
Additional information:
Deprecated alias names for this type: N/A
Magic number(s): N/A
File extension(s): None
Macintosh file type code(s): "TEXT"
Bierman, et al. Standards Track PAGE 23
RFC 8072 YANG Patch February 2017
Person & email address to contact for further information: See
the Authors' Addresses section of RFC 8072.
Intended usage: COMMON
Restrictions on usage: N/A
Author: See the Authors' Addresses section of RFC 8072.
Change controller: Internet Engineering Task Force
(mailto:iesg@ietf.org).
Provisional registration? (standards tree only): no
4.2.2. Media Type "application/yang-patch+json"
Type name: application
Subtype name: yang-patch+json
Required parameters: None
Optional parameters: None
Encoding considerations: 8-bit
The "utf-8" charset is always used for this type.
Each conceptual YANG data node is encoded according to
RFC 7951. A metadata annotation is encoded according to
RFC 7952. In addition, the "yang-patch" YANG Patch
template found in RFC 8072 defines the structure of a
YANG Patch request.
Security considerations: Security considerations related
to the generation and consumption of RESTCONF messages
are discussed in Section 5 of RFC 8072.
Additional security considerations are specific to the
semantics of particular YANG data models. Each YANG module
is expected to specify security considerations for the
YANG data defined in that module.
Interoperability considerations: RFC 8072 specifies the format
of conforming messages and the interpretation thereof.
Published specification: RFC 8072
Applications that use this media type: Instance document
data parsers used within a protocol or automation tool
that utilize the YANG Patch data structure.
Bierman, et al. Standards Track PAGE 24
RFC 8072 YANG Patch February 2017
Fragment identifier considerations: The syntax and semantics
of fragment identifiers are the same as the syntax and semantics
specified for the "application/json" media type.
Additional information:
Deprecated alias names for this type: N/A
Magic number(s): N/A
File extension(s): None
Macintosh file type code(s): "TEXT"
Person & email address to contact for further information: See
the Authors' Addresses section of RFC 8072.
Intended usage: COMMON
Restrictions on usage: N/A
Author: See the Authors' Addresses section of RFC 8072.
Change controller: Internet Engineering Task Force
(mailto:iesg@ietf.org).
Provisional registration? (standards tree only): no
4.3. RESTCONF Capability URNs
This document registers one capability identifier in the "RESTCONF
Capability URNs" registry [RFC 8040]. The review policy for this
registry is "IETF Review" [RFC 5226].
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 [RFC 8040]. This
document defines edit processing instructions for a variant of the
PATCH method, as used within the RESTCONF protocol. Message
integrity is provided by the RESTCONF protocol. There is no
additional capability to validate that a patch has not been altered.
It may be possible to use YANG Patch with other protocols besides
RESTCONF; this topic is outside the scope of this document.
Bierman, et al. Standards Track PAGE 25
RFC 8072 YANG Patch February 2017
For RESTCONF, both the client and server MUST be authenticated
according to Section 2 of [RFC 8040]. It is important for RESTCONF
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 PATCH request MUST be applied atomically, as specified in Section 2
of [RFC 5789].
A RESTCONF server implementation SHOULD attempt to prevent system
disruption due to incremental processing of the YANG Patch
"edit" list. It may be possible to construct an attack on such a
RESTCONF server, which relies on the edit processing order mandated
by YANG Patch. A server SHOULD apply only the fully validated
configuration to the underlying system. For example, an "edit" list
that deleted an interface and then recreated it could cause system
disruption if the "edit" list was incrementally applied.
A RESTCONF server implementation SHOULD attempt to prevent system
disruption due to excessive resource consumption required to fulfill
YANG Patch edit requests. On such an implementation, it may be
possible to construct an attack that attempts to consume all
available memory or other resource types.
6. References
6.1. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<http://www.rfc-editor.org/info/RFC 2119>.
[RFC 3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC 3688, January 2004,
<http://www.rfc-editor.org/info/RFC 3688>.
[RFC 5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, DOI 10.17487/RFC 5789, March 2010,
<http://www.rfc-editor.org/info/RFC 5789>.
[RFC 6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC 6020, October 2010,
<http://www.rfc-editor.org/info/RFC 6020>.
Bierman, et al. Standards Track PAGE 26
RFC 8072 YANG Patch February 2017
[RFC 6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC 6241, June 2011,
<http://www.rfc-editor.org/info/RFC 6241>.
[RFC 7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC 7159,
March 2014, <http://www.rfc-editor.org/info/RFC 7159>.
[RFC 7230] Fielding, R., Ed., and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC 7230, June 2014,
<http://www.rfc-editor.org/info/RFC 7230>.
[RFC 7231] Fielding, R., Ed., and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Semantics and Content",
RFC 7231, DOI 10.17487/RFC 7231, June 2014,
<http://www.rfc-editor.org/info/RFC 7231>.
[RFC 7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC 7950, August 2016,
<http://www.rfc-editor.org/info/RFC 7950>.
[RFC 7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC 7951, August 2016,
<http://www.rfc-editor.org/info/RFC 7951>.
[RFC 7952] Lhotka, L., "Defining and Using Metadata with YANG",
RFC 7952, DOI 10.17487/RFC 7952, August 2016,
<http://www.rfc-editor.org/info/RFC 7952>.
[RFC 8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC 8040, January 2017,
<http://www.rfc-editor.org/info/RFC 8040>.
[W3C.REC-xml-20081126]
Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
F. Yergeau, "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>.
6.2. Informative References
[RFC 5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC 5226, May 2008,
<http://www.rfc-editor.org/info/RFC 5226>.
Bierman, et al. Standards Track PAGE 27
RFC 8072 YANG Patch February 2017
Appendix A. 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 [RFC 8040].
YANG tree diagram for the "example-jukebox" module:
+--rw jukebox!
+--rw library
| +--rw artist* [name]
| | +--rw name string
| | +--rw album* [name]
| | +--rw name string
| | +--rw genre? identityref
| | +--rw year? uint16
| | +--rw admin
| | | +--rw label? string
| | | +--rw catalogue-number? string
| | +--rw song* [name]
| | +--rw name string
| | +--rw location string
| | +--rw format? string
| | +--rw length? uint32
| +--ro artist-count? uint32
| +--ro album-count? uint32
| +--ro song-count? uint32
+--rw playlist* [name]
| +--rw name string
| +--rw description? string
| +--rw song* [index]
| +--rw index uint32
| +--rw id instance-identifier
+--rw player
+--rw gap? decimal64
rpcs:
+---x play
+--ro input
+--ro playlist string
+--ro song-number uint32
Bierman, et al. Standards Track PAGE 28
RFC 8072 YANG Patch February 2017
A.1. YANG Patch Examples
This section includes RESTCONF examples. Most examples are shown in
JSON encoding [RFC 7159], and some are shown in XML encoding
[W3C.REC-xml-20081126].
A.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. XML encoding is
used in this example.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\
library/artist=Foo%20Fighters/album=Wasting%20Light HTTP/1.1
Host: example.com
Accept: application/yang-data+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=Bridge%20Burning</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>
Bierman, et al. Standards Track PAGE 29
RFC 8072 YANG Patch February 2017
<edit>
<edit-id>edit2</edit-id>
<operation>create</operation>
<target>/song=Rope</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=Dear%20Rosemary</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>
Bierman, et al. Standards Track PAGE 30
RFC 8072 YANG Patch February 2017
XML response from the RESTCONF server:
HTTP/1.1 409 Conflict
Date: Thu, 26 Jan 2017 20:56:30 GMT
Server: example-server
Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT
Content-Type: application/yang-data+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='Bridge Burning']
</error-path>
<error-message>
Data already exists; cannot be created
</error-message>
</error>
</errors>
</edit>
</edit-status>
</yang-patch-status>
Bierman, et al. Standards Track PAGE 31
RFC 8072 YANG Patch February 2017
JSON response from the RESTCONF 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 specified in [RFC 7951] is used.
HTTP/1.1 409 Conflict
Date: Thu, 26 Jan 2017 20:56:30 GMT
Server: example-server
Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT
Content-Type: application/yang-data+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='Bridge Burning']",
"error-message":
"Data already exists; cannot be created"
}
]
}
}
]
}
}
}
Bierman, et al. Standards Track PAGE 32
RFC 8072 YANG Patch February 2017
A.1.2. Add Resources: Success
The following example shows several songs being added to an existing
album.
o Each of two edits contains one song.
o Both edits succeed, and new sub-resources are created.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\
library/artist=Foo%20Fighters/album=Wasting%20Light \
HTTP/1.1
Host: example.com
Accept: application/yang-data+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=Rope",
"value" : {
"song" : [
{
"name" : "Rope",
"location" : "/media/rope.mp3",
"format" : "MP3",
"length" : 259
}
]
}
},
Bierman, et al. Standards Track PAGE 33
RFC 8072 YANG Patch February 2017
{
"edit-id" : "edit2",
"operation" : "create",
"target" : "/song=Dear%20Rosemary",
"value" : {
"song" : [
{
"name" : "Dear Rosemary",
"location" : "/media/dear_rosemary.mp3",
"format" : "MP3",
"length" : 269
}
]
}
}
]
}
}
Response from the RESTCONF server:
HTTP/1.1 200 OK
Date: Thu, 26 Jan 2017 20:56:30 GMT
Server: example-server
Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT
Content-Type: application/yang-data+json
{
"ietf-yang-patch:yang-patch-status" : {
"patch-id" : "add-songs-patch-2",
"ok" : [null]
}
}
Bierman, et al. Standards Track PAGE 34
RFC 8072 YANG Patch February 2017
A.1.3. Insert List Entry
The following example shows a song being inserted within an existing
playlist. Song "6" in playlist "Foo-One" is being inserted after
song "5" in the playlist. The operation succeeds, so a non-error
reply can be provided.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\
playlist=Foo-One HTTP/1.1
Host: example.com
Accept: application/yang-data+json
Content-Type: application/yang-patch+json
{
"ietf-yang-patch:yang-patch" : {
"patch-id" : "insert-song-patch",
"comment" : "Insert song 6 after song 5",
"edit" : [
{
"edit-id" : "edit1",
"operation" : "insert",
"target" : "/song=6",
"point" : "/song=5",
"where" : "after",
"value" : {
"example-jukebox:song" : [
{
"index" : 6,
"id" : "/example-jukebox:jukebox/library\
/artist[name='Foo Fighters']\
/album[name='Wasting Light']\
/song[name='Bridge Burning']"
}
]
}
}
]
}
Bierman, et al. Standards Track PAGE 35
RFC 8072 YANG Patch February 2017
Response from the RESTCONF server:
HTTP/1.1 200 OK
Date: Thu, 26 Jan 2017 20:56:30 GMT
Server: example-server
Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT
Content-Type: application/yang-data+json
{
"ietf-yang-patch:yang-patch-status" : {
"patch-id" : "insert-song-patch",
"ok" : [null]
}
}
A.1.4. Move List Entry
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. Note that no "value" parameter is needed
for a "move" operation. The operation succeeds, so a non-error reply
can be provided.
Request from the RESTCONF client:
PATCH /restconf/data/example-jukebox:jukebox/\
playlist=Foo-One HTTP/1.1
Host: example.com
Accept: application/yang-data+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" : "/song=3",
"where" : "after"
}
]
}
}
Bierman, et al. Standards Track PAGE 36
RFC 8072 YANG Patch February 2017
Response from the RESTCONF server:
HTTP/1.1 200 OK
Date: Thu, 26 Jan 2017 20:56:30 GMT
Server: example-server
Last-Modified: Thu, 26 Jan 2017 20:56:30 GMT
Content-Type: application/yang-data+json
{
"ietf-restconf:yang-patch-status" : {
"patch-id" : "move-song-patch",
"ok" : [null]
}
}
A.1.5. Edit Datastore Resource
The following example shows how three top-level data nodes from
different modules can be edited at the same time.
Example module "foo" defines leaf X. Example module "bar" defines
container Y, with child leafs A and B. Example module "baz" defines
list Z, with key C and child leafs D and E.
Request from the RESTCONF client:
PATCH /restconf/data HTTP/1.1
Host: example.com
Accept: application/yang-data+json
Content-Type: application/yang-patch+json
{
"ietf-yang-patch:yang-patch" : {
"patch-id" : "datastore-patch-1",
"comment" : "Edit 3 top-level data nodes at once",
"edit" : [
{
"edit-id" : "edit1",
"operation" : "create",
"target" : "/foo:X",
"value" : {
"foo:X" : 42
}
},
Bierman, et al. Standards Track PAGE 37
RFC 8072 YANG Patch February 2017
{
"edit-id" : "edit2",
"operation" : "merge",
"target" : "/bar:Y",
"value" : {
"bar:Y" : {
"A" : "test1",
"B" : 99
}
}
},
{
"edit-id" : "edit3",
"operation" : "replace",
"target" : "/baz:Z=2",
"value" : {
"baz:Z" : [
{
"C" : 2,
"D" : 100,
"E" : false
}
]
}
}
]
}
}
Response from the RESTCONF server:
HTTP/1.1 200 OK
Date: Thu, 26 Jan 2017 20:56:30 GMT
Server: example-server
Last-Modified: Thu, 26 Jan 2017 20:55:30 GMT
Content-Type: application/yang-data+json
{
"ietf-yang-patch:yang-patch-status" : {
"patch-id" : "datastore-patch-1",
"ok" : [null]
}
}
Bierman, et al. Standards Track PAGE 38
RFC 8072 YANG Patch February 2017
Acknowledgements
The authors would like to thank Rex Fernando for his contributions to
this document.
Contributions to this material by Andy Bierman are based upon work
supported by the United States Army, Space & Terrestrial
Communications Directorate (S&TCD) under Contract
No. W15P7T-13-C-A616. Any opinions, findings, and conclusions or
recommendations expressed in this material are those of the author(s)
and do not necessarily reflect the views of the S&TCD.
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
Bierman, et al. Standards Track PAGE 39
RFC TOTAL SIZE: 65765 bytes
PUBLICATION DATE: Wednesday, February 22nd, 2017
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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