7951
PROPOSED STANDARD
JSON Encoding of Data Modeled with YANG
Authors: L. Lhotka
Date: August 2016
Area: ops
Working Group: netmod
Stream: IETF
Abstract
This document defines encoding rules for representing configuration data, state data, parameters of Remote Procedure Call (RPC) operations or actions, and notifications defined using YANG as JavaScript Object Notation (JSON) text.
RFC 7951
PROPOSED STANDARD
Errata Exist
Internet Engineering Task Force (IETF) L. Lhotka
Request for Comments: 7951 CZ.NIC
Category: Standards Track August 2016
ISSN: 2070-1721
<span class="h1">JSON Encoding of Data Modeled with YANG</span>
Abstract
This document defines encoding rules for representing configuration
data, state data, parameters of Remote Procedure Call (RPC)
operations or actions, and notifications defined using YANG as
JavaScript Object Notation (JSON) text.
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 <a href="./rfc7841#section-2">Section 2 of RFC 7841</a>.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
<a href="https://www.rfc-editor.org/info/rfc7951">http://www.rfc-editor.org/info/rfc7951</a>.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) 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.
<span class="grey">Lhotka Standards Track [Page 1]</span><span id="page-2" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
Table of Contents
<a href="#section-1">1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a>
<a href="#section-2">2</a>. Terminology and Notation . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a>
<a href="#section-3">3</a>. Properties of the JSON Encoding . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-4">4</a>. Names and Namespaces . . . . . . . . . . . . . . . . . . . . <a href="#page-5">5</a>
<a href="#section-5">5</a>. Encoding of YANG Data Node Instances . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-5.1">5.1</a>. The "leaf" Data Node . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-5.2">5.2</a>. The "container" Data Node . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-5.3">5.3</a>. The "leaf-list" Data Node . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-5.4">5.4</a>. The "list" Data Node . . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-5.5">5.5</a>. The "anydata" Data Node . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-5.6">5.6</a>. The "anyxml" Data Node . . . . . . . . . . . . . . . . . <a href="#page-10">10</a>
<a href="#section-5.7">5.7</a>. Metadata Objects . . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6">6</a>. Representing YANG Data Types in JSON Values . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6.1">6.1</a>. Numeric Types . . . . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6.2">6.2</a>. The "string" Type . . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6.3">6.3</a>. The "boolean" Type . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6.4">6.4</a>. The "enumeration" Type . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-6.5">6.5</a>. The "bits" Type . . . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-6.6">6.6</a>. The "binary" Type . . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-6.7">6.7</a>. The "leafref" Type . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-6.8">6.8</a>. The "identityref" Type . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-6.9">6.9</a>. The "empty" Type . . . . . . . . . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-6.10">6.10</a>. The "union" Type . . . . . . . . . . . . . . . . . . . . <a href="#page-14">14</a>
<a href="#section-6.11">6.11</a>. The "instance-identifier" Type . . . . . . . . . . . . . <a href="#page-15">15</a>
<a href="#section-7">7</a>. I-JSON Compliance . . . . . . . . . . . . . . . . . . . . . . <a href="#page-15">15</a>
<a href="#section-8">8</a>. Security Considerations . . . . . . . . . . . . . . . . . . . <a href="#page-16">16</a>
<a href="#section-9">9</a>. References . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-16">16</a>
<a href="#section-9.1">9.1</a>. Normative References . . . . . . . . . . . . . . . . . . <a href="#page-16">16</a>
<a href="#section-9.2">9.2</a>. Informative References . . . . . . . . . . . . . . . . . <a href="#page-17">17</a>
<a href="#appendix-A">Appendix A</a>. A Complete Example . . . . . . . . . . . . . . . . . <a href="#page-18">18</a>
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-20">20</a>
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-20">20</a>
<span class="grey">Lhotka Standards Track [Page 2]</span><span id="page-3" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
The Network Configuration Protocol (NETCONF) [<a href="./rfc6241" title=""Network Configuration Protocol (NETCONF)"">RFC6241</a>] uses XML [<a href="#ref-XML" title=""Extensible Markup Language (XML) 1.0 (Fifth Edition)"">XML</a>]
for encoding data in its Content Layer. Other management protocols
might want to use other encodings while still benefiting from using
YANG [<a href="./rfc7950" title=""The YANG 1.1 Data Modeling Language"">RFC7950</a>] as the data modeling language.
For example, the RESTCONF protocol [<a href="#ref-RESTCONF" title=""RESTCONF Protocol"">RESTCONF</a>] supports two encodings:
XML (media type "application/yang.data+xml") and JavaScript Object
Notation (JSON) (media type "application/yang.data+json").
The specification of the YANG 1.1 data modeling language [<a href="./rfc7950" title=""The YANG 1.1 Data Modeling Language"">RFC7950</a>]
defines only XML encoding of data trees, i.e., configuration data,
state data, input/output parameters of Remote Procedure Call (RPC)
operations or actions, and notifications. The aim of this document
is to define rules for encoding the same data as JSON text [<a href="./rfc7159" title=""The JavaScript Object Notation (JSON) Data Interchange Format"">RFC7159</a>].
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Terminology and Notation</span>
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 [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>].
The following terms are defined in [<a href="./rfc7950" title=""The YANG 1.1 Data Modeling Language"">RFC7950</a>]:
o action
o anydata
o anyxml
o augment
o container
o data node
o data tree
o identity
o instance identifier
o leaf
o leaf-list
o list
<span class="grey">Lhotka Standards Track [Page 3]</span><span id="page-4" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
o module
o RPC operation
o submodule
The following terms are defined in [<a href="./rfc6241" title=""Network Configuration Protocol (NETCONF)"">RFC6241</a>]:
o configuration data
o notification
o state data
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Properties of the JSON Encoding</span>
This document defines JSON encoding for YANG data trees and their
subtrees. It is always assumed that the top-level structure in JSON-
encoded data is an object.
Instances of YANG data nodes (leafs, containers, leaf-lists, lists,
anydata nodes, and anyxml nodes) are encoded as members of a JSON
object, i.e., name/value pairs. <a href="#section-4">Section 4</a> defines how the name part
is formed, and the following sections deal with the value part. The
encoding rules are identical for all types of data trees, i.e.,
configuration data, state data, parameters of RPC operations,
actions, and notifications.
With the exception of "anydata" encoding (<a href="#section-5.5">Section 5.5</a>), all rules in
this document are also applicable to YANG 1.0 [<a href="./rfc6020" title=""YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)"">RFC6020</a>].
Unlike XML element content, JSON values carry partial type
information (number, string, boolean). The JSON encoding is defined
so that this information is never in conflict with the data type of
the corresponding YANG leaf or leaf-list.
With the exception of anyxml and schema-less anydata nodes, it is
possible to map a JSON-encoded data tree to XML encoding as defined
in [<a href="./rfc7950" title=""The YANG 1.1 Data Modeling Language"">RFC7950</a>], and vice versa. However, such conversions require the
YANG data model to be available.
In order to achieve maximum interoperability while allowing
implementations to use a variety of existing JSON parsers, the JSON
encoding rules follow, as much as possible, the constraints of the
I-JSON (Internet JSON) restricted profile [<a href="./rfc7493" title=""The I-JSON Message Format"">RFC7493</a>]. <a href="#section-7">Section 7</a>
discusses I-JSON conformance in more detail.
<span class="grey">Lhotka Standards Track [Page 4]</span><span id="page-5" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Names and Namespaces</span>
A JSON object member name MUST be in one of the following forms:
o simple - identical to the identifier of the corresponding YANG
data node.
o namespace-qualified - the data node identifier is prefixed with
the name of the module in which the data node is defined,
separated from the data node identifier by the colon character
(":").
The name of a module determines the namespace of all data node names
defined in that module. If a data node is defined in a submodule,
then the namespace-qualified member name uses the name of the main
module to which the submodule belongs.
ABNF syntax [<a href="./rfc5234" title=""Augmented BNF for Syntax Specifications: ABNF"">RFC5234</a>] of a member name is shown in Figure 1, where
the production for "identifier" is defined in <a href="./rfc7950#section-14">Section 14 of
[RFC7950]</a>.
member-name = [identifier ":"] identifier
Figure 1: ABNF Production for a JSON Member Name
A namespace-qualified member name MUST be used for all members of a
top-level JSON object and then also whenever the namespaces of the
data node and its parent node are different. In all other cases, the
simple form of the member name MUST be used.
For example, consider the following YANG module:
module example-foomod {
namespace "http://example.com/foomod";
prefix "foomod";
container top {
leaf foo {
type uint8;
}
}
}
<span class="grey">Lhotka Standards Track [Page 5]</span><span id="page-6" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
If the data model consists only of this module, then the following is
valid JSON-encoded configuration data:
{
"example-foomod:top": {
"foo": 54
}
}
Note that the member of the top-level object uses the namespace-
qualified name but the "foo" leaf doesn't because it is defined in
the same module as its parent container "top".
Now, assume that the container "top" is augmented from another
module, "example-barmod":
module example-barmod {
namespace "http://example.com/barmod";
prefix "barmod";
import example-foomod {
prefix "foomod";
}
augment "/foomod:top" {
leaf bar {
type boolean;
}
}
}
Valid JSON-encoded configuration data containing both leafs may then
look like this:
{
"example-foomod:top": {
"foo": 54,
"example-barmod:bar": true
}
}
The name of the "bar" leaf is prefixed with the namespace identifier
because its parent is defined in a different module.
<span class="grey">Lhotka Standards Track [Page 6]</span><span id="page-7" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
Explicit namespace identifiers are sometimes needed when encoding
values of the "identityref" and "instance-identifier" types. The
same form of namespace-qualified name as defined above is then used.
See Sections <a href="#section-6.8">6.8</a> and <a href="#section-6.11">6.11</a> for details.
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Encoding of YANG Data Node Instances</span>
Every data node instance is encoded as a name/value pair where the
name is formed from the data node identifier using the rules of
<a href="#section-4">Section 4</a>. The value depends on the category of the data node, as
explained in the following subsections.
Character encoding MUST be UTF-8.
<span class="h3"><a class="selflink" id="section-5.1" href="#section-5.1">5.1</a>. The "leaf" Data Node</span>
A leaf instance is encoded as a name/value pair where the value can
be a string, number, literal "true" or "false", or the special array
"[null]", depending on the type of the leaf (see <a href="#section-6">Section 6</a> for the
type encoding rules).
Example: For the leaf node definition
leaf foo {
type uint8;
}
the following is a valid JSON-encoded instance:
"foo": 123
<span class="grey">Lhotka Standards Track [Page 7]</span><span id="page-8" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h3"><a class="selflink" id="section-5.2" href="#section-5.2">5.2</a>. The "container" Data Node</span>
A container instance is encoded as a name/object pair. The
container's child data nodes are encoded as members of the object.
Example: For the container definition
container bar {
leaf foo {
type uint8;
}
}
the following is a valid JSON-encoded instance:
"bar": {
"foo": 123
}
<span class="h3"><a class="selflink" id="section-5.3" href="#section-5.3">5.3</a>. The "leaf-list" Data Node</span>
A leaf-list is encoded as a name/array pair, and the array elements
are values of some scalar type, which can be a string, number,
literal "true" or "false", or the special array "[null]", depending
on the type of the leaf-list (see <a href="#section-6">Section 6</a> for the type encoding
rules).
The ordering of array elements follows the same rules as the ordering
of XML elements representing leaf-list entries in the XML encoding.
Specifically, the "ordered-by" properties (<a href="./rfc7950#section-7.7.7">Section 7.7.7 in
[RFC7950]</a>) MUST be observed.
Example: For the leaf-list definition
leaf-list foo {
type uint8;
}
the following is a valid JSON-encoded instance:
"foo": [123, 0]
<span class="grey">Lhotka Standards Track [Page 8]</span><span id="page-9" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h3"><a class="selflink" id="section-5.4" href="#section-5.4">5.4</a>. The "list" Data Node</span>
A list instance is encoded as a name/array pair, and the array
elements are JSON objects.
The ordering of array elements follows the same rules as the ordering
of XML elements representing list entries in the XML encoding.
Specifically, the "ordered-by" properties (<a href="./rfc7950#section-7.7.7">Section 7.7.7 in
[RFC7950]</a>) MUST be observed.
Unlike the XML encoding, where list keys are required to precede any
other siblings within a list entry and appear in the order specified
by the data model, the order of members in a JSON-encoded list entry
is arbitrary because JSON objects are fundamentally unordered
collections of members.
Example: For the list definition
list bar {
key foo;
leaf foo {
type uint8;
}
leaf baz {
type string;
}
}
the following is a valid JSON-encoded instance:
"bar": [
{
"foo": 123,
"baz": "zig"
},
{
"baz": "zag",
"foo": 0
}
]
<span class="h3"><a class="selflink" id="section-5.5" href="#section-5.5">5.5</a>. The "anydata" Data Node</span>
The anydata data node serves as a container for an arbitrary set of
nodes that otherwise appear as normal YANG-modeled data. A data
model for anydata content may or may not be known at runtime. In the
latter case, converting JSON-encoded instances to the XML encoding
defined in [<a href="./rfc7950" title=""The YANG 1.1 Data Modeling Language"">RFC7950</a>] may be impossible.
<span class="grey">Lhotka Standards Track [Page 9]</span><span id="page-10" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
An anydata instance is encoded in the same way as a container, i.e.,
as a name/object pair. The requirement that anydata content can be
modeled by YANG implies the following rules for the JSON text inside
the object:
o It is valid I-JSON [<a href="./rfc7493" title=""The I-JSON Message Format"">RFC7493</a>].
o All object member names satisfy the ABNF production in Figure 1.
o Any JSON array contains either only unique scalar values (as a
leaf-list; see <a href="#section-5.3">Section 5.3</a>) or only objects (as a list; see
<a href="#section-5.4">Section 5.4</a>).
o The "null" value is only allowed in the single-element array
"[null]" corresponding to the encoding of the "empty" type; see
<a href="#section-6.9">Section 6.9</a>.
Example: For the anydata definition
anydata data;
the following is a valid JSON-encoded instance:
"data": {
"ietf-notification:notification": {
"eventTime": "2014-07-29T13:43:01Z",
"example-event:event": {
"event-class": "fault",
"reporting-entity": {
"card": "Ethernet0"
},
"severity": "major"
}
}
}
<span class="h3"><a class="selflink" id="section-5.6" href="#section-5.6">5.6</a>. The "anyxml" Data Node</span>
An anyxml instance is encoded as a JSON name/value pair. The value
MUST satisfy I-JSON constraints.
Example: For the anyxml definition
anyxml bar;
the following is a valid JSON-encoded instance:
"bar": [true, null, true]
<span class="grey">Lhotka Standards Track [Page 10]</span><span id="page-11" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h3"><a class="selflink" id="section-5.7" href="#section-5.7">5.7</a>. Metadata Objects</span>
Apart from instances of YANG data nodes, a JSON document MAY contain
special object members whose name starts with the "@" character
(COMMERCIAL AT). Such members are used for special purposes, such as
encoding metadata [<a href="./rfc7952" title=""Defining and Using Metadata with YANG"">RFC7952</a>]. The exact syntax and semantics of such
members are outside the scope of this document.
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Representing YANG Data Types in JSON Values</span>
The type of the JSON value in an instance of the leaf or leaf-list
data node depends on the type of that data node, as specified in the
following subsections.
<span class="h3"><a class="selflink" id="section-6.1" href="#section-6.1">6.1</a>. Numeric Types</span>
A value of the "int8", "int16", "int32", "uint8", "uint16", or
"uint32" type is represented as a JSON number.
A value of the "int64", "uint64", or "decimal64" type is represented
as a JSON string whose content is the lexical representation of the
corresponding YANG type as specified in Sections <a href="#section-9.2.1">9.2.1</a> and <a href="#section-9.3.1">9.3.1</a> of
[<a href="./rfc7950" title=""The YANG 1.1 Data Modeling Language"">RFC7950</a>].
For example, if the type of the leaf "foo" in <a href="#section-5.1">Section 5.1</a> was
"uint64" instead of "uint8", the instance would have to be encoded as
"foo": "123"
The special handling of 64-bit numbers follows from the I-JSON
recommendation to encode numbers exceeding the IEEE 754-2008
double-precision range [<a href="#ref-IEEE754-2008">IEEE754-2008</a>] as strings; see <a href="./rfc7493#section-2.2">Section 2.2 in
[RFC7493]</a>.
<span class="h3"><a class="selflink" id="section-6.2" href="#section-6.2">6.2</a>. The "string" Type</span>
A "string" value is represented as a JSON string, subject to JSON
string encoding rules.
<span class="h3"><a class="selflink" id="section-6.3" href="#section-6.3">6.3</a>. The "boolean" Type</span>
A "boolean" value is represented as the corresponding JSON literal
name "true" or "false".
<span class="grey">Lhotka Standards Track [Page 11]</span><span id="page-12" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h3"><a class="selflink" id="section-6.4" href="#section-6.4">6.4</a>. The "enumeration" Type</span>
An "enumeration" value is represented as a JSON string -- one of the
names assigned by "enum" statements in YANG.
The representation is identical to the lexical representation of the
"enumeration" type in XML; see <a href="./rfc7950#section-9.6">Section 9.6 in [RFC7950]</a>.
<span class="h3"><a class="selflink" id="section-6.5" href="#section-6.5">6.5</a>. The "bits" Type</span>
A "bits" value is represented as a JSON string -- a space-separated
sequence of names of bits that are set. The permitted bit names are
assigned by "bit" statements in YANG.
The representation is identical to the lexical representation of the
"bits" type; see <a href="./rfc7950#section-9.7">Section 9.7 in [RFC7950]</a>.
<span class="h3"><a class="selflink" id="section-6.6" href="#section-6.6">6.6</a>. The "binary" Type</span>
A "binary" value is represented as a JSON string -- base64 encoding
of arbitrary binary data.
The representation is identical to the lexical representation of the
"binary" type in XML; see <a href="./rfc7950#section-9.8">Section 9.8 in [RFC7950]</a>.
<span class="h3"><a class="selflink" id="section-6.7" href="#section-6.7">6.7</a>. The "leafref" Type</span>
A "leafref" value is represented using the same rules as the type of
the leaf to which the leafref value refers.
<span class="h3"><a class="selflink" id="section-6.8" href="#section-6.8">6.8</a>. The "identityref" Type</span>
An "identityref" value is represented as a string -- the name of an
identity. If the identity is defined in a module other than the leaf
node containing the identityref value, the namespace-qualified form
(<a href="#section-4">Section 4</a>) MUST be used. Otherwise, both the simple and namespace-
qualified forms are permitted.
<span class="grey">Lhotka Standards Track [Page 12]</span><span id="page-13" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
For example, consider the following schematic module:
module example-mod {
...
import ietf-interfaces {
prefix if;
}
...
leaf type {
type identityref {
base "if:interface-type";
}
}
}
A valid instance of the "type" leaf is then encoded as follows:
"type": "iana-if-type:ethernetCsmacd"
The namespace identifier "iana-if-type" must be present in this case
because the "ethernetCsmacd" identity is not defined in the same
module as the "type" leaf.
<span class="h3"><a class="selflink" id="section-6.9" href="#section-6.9">6.9</a>. The "empty" Type</span>
An "empty" value is represented as "[null]", i.e., an array with the
"null" literal being its only element. For the purposes of this
document, "[null]" is considered an atomic scalar value.
This encoding of the "empty" type was chosen instead of using simply
"null" in order to facilitate the use of empty leafs in common
programming languages where the "null" value of a member is treated
as if the member is not present.
Example: For the leaf definition
leaf foo {
type empty;
}
a valid instance is
"foo": [null]
<span class="grey">Lhotka Standards Track [Page 13]</span><span id="page-14" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h3"><a class="selflink" id="section-6.10" href="#section-6.10">6.10</a>. The "union" Type</span>
A value of the "union" type is encoded as the value of any of the
member types.
When validating a value of the "union" type, the type information
conveyed by the JSON encoding MUST also be taken into account. JSON
syntax thus provides additional means for resolving the member type
of the union that are not available in XML encoding.
For example, consider the following YANG definition:
leaf bar {
type union {
type uint16;
type string;
}
}
In RESTCONF [<a href="#ref-RESTCONF" title=""RESTCONF Protocol"">RESTCONF</a>], it is possible to set the value of "bar" in
the following way when using the "application/yang.data+xml"
media type:
<bar>13.5</bar>
because the value may be interpreted as a string, i.e., the
second member type of the union. When using the
"application/yang.data+json" media type, however, this is an error:
"bar": 13.5
In this case, the JSON encoding indicates that the value is supposed
to be a number rather than a string, and it is not a valid "uint16"
value.
Conversely, the value of
"bar": "1"
is to be interpreted as a string.
<span class="grey">Lhotka Standards Track [Page 14]</span><span id="page-15" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h3"><a class="selflink" id="section-6.11" href="#section-6.11">6.11</a>. The "instance-identifier" Type</span>
An "instance-identifier" value is encoded as a string that is
analogical to the lexical representation in XML encoding; see
<a href="./rfc7950#section-9.13.2">Section 9.13.2 in [RFC7950]</a>. However, the encoding of namespaces in
instance-identifier values follows the rules stated in <a href="#section-4">Section 4</a>,
namely:
o The leftmost (top-level) data node name is always in the
namespace-qualified form.
o Any subsequent data node name is in the namespace-qualified form
if the node is defined in a module other than its parent node, and
the simple form is used otherwise. This rule also holds for node
names appearing in predicates.
For example,
/ietf-interfaces:interfaces/interface[name='eth0']/ietf-ip:ipv4/ip
is a valid instance-identifier value because the data nodes
"interfaces", "interface", and "name" are defined in the module
"ietf-interfaces", whereas "ipv4" and "ip" are defined in "ietf-ip".
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. I-JSON Compliance</span>
I-JSON [<a href="./rfc7493" title=""The I-JSON Message Format"">RFC7493</a>] is a restricted profile of JSON that guarantees
maximum interoperability for protocols that use JSON in their
messages, no matter what JSON encoders/decoders are used in protocol
implementations. The encoding defined in this document therefore
observes the I-JSON requirements and recommendations as closely as
possible.
In particular, the following properties are guaranteed:
o Character encoding is UTF-8.
o Member names within the same JSON object are always unique.
o The order of JSON object members is never relied upon.
o Numbers of any type supported by YANG can be exchanged reliably.
See <a href="#section-6.1">Section 6.1</a> for details.
The JSON encoding defined in this document deviates from I-JSON only
in the representation of the "binary" type. In order to remain
compatible with XML encoding, the base64 encoding scheme is used
(<a href="#section-6.6">Section 6.6</a>), whilst I-JSON recommends base64url instead.
<span class="grey">Lhotka Standards Track [Page 15]</span><span id="page-16" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. Security Considerations</span>
This document defines an alternative encoding for data modeled in the
YANG data modeling language. As such, it doesn't contribute any new
security issues beyond those discussed in <a href="./rfc7950#section-17">Section 17 of [RFC7950]</a>.
This document defines no mechanisms for signing and encrypting data
modeled with YANG. Under normal circumstances, data security and
integrity are guaranteed by the management protocol in use, such as
NETCONF [<a href="./rfc6241" title=""Network Configuration Protocol (NETCONF)"">RFC6241</a>] or RESTCONF [<a href="#ref-RESTCONF" title=""RESTCONF Protocol"">RESTCONF</a>]. If this is not the case,
external mechanisms, such as Public-Key Cryptography Standards (PKCS)
#7 [<a href="./rfc2315" title=""PKCS #7: Cryptographic Message Syntax Version 1.5"">RFC2315</a>] or JSON Object Signing and Encryption (JOSE) [<a href="./rfc7515" title=""JSON Web Signature (JWS)"">RFC7515</a>]
[<a href="./rfc7516" title=""JSON Web Encryption (JWE)"">RFC7516</a>], need to be considered.
JSON processing is rather different from XML, and JSON parsers may
thus suffer from different types of vulnerabilities than their XML
counterparts. To minimize these new security risks, software on the
receiving side SHOULD reject all messages that do not comply with the
rules of this document and reply with an appropriate error message to
the sender.
<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. References</span>
<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>. Normative References</span>
[<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>,
DOI 10.17487/RFC2119, March 1997,
<<a href="https://www.rfc-editor.org/info/rfc2119">http://www.rfc-editor.org/info/rfc2119</a>>.
[<a id="ref-RFC5234">RFC5234</a>] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, <a href="./rfc5234">RFC 5234</a>,
DOI 10.17487/RFC5234, January 2008,
<<a href="https://www.rfc-editor.org/info/rfc5234">http://www.rfc-editor.org/info/rfc5234</a>>.
[<a id="ref-RFC6241">RFC6241</a>] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", <a href="./rfc6241">RFC 6241</a>, DOI 10.17487/RFC6241, June 2011,
<<a href="https://www.rfc-editor.org/info/rfc6241">http://www.rfc-editor.org/info/rfc6241</a>>.
[<a id="ref-RFC7159">RFC7159</a>] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", <a href="./rfc7159">RFC 7159</a>, DOI 10.17487/RFC7159, March
2014, <<a href="https://www.rfc-editor.org/info/rfc7159">http://www.rfc-editor.org/info/rfc7159</a>>.
[<a id="ref-RFC7493">RFC7493</a>] Bray, T., Ed., "The I-JSON Message Format", <a href="./rfc7493">RFC 7493</a>,
DOI 10.17487/RFC7493, March 2015,
<<a href="https://www.rfc-editor.org/info/rfc7493">http://www.rfc-editor.org/info/rfc7493</a>>.
<span class="grey">Lhotka Standards Track [Page 16]</span><span id="page-17" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
[<a id="ref-RFC7950">RFC7950</a>] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
<a href="./rfc7950">RFC 7950</a>, DOI 10.17487/RFC7950, August 2016,
<<a href="https://www.rfc-editor.org/info/rfc7950">http://www.rfc-editor.org/info/rfc7950</a>>.
<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>. Informative References</span>
[<a id="ref-IEEE754-2008">IEEE754-2008</a>]
IEEE, "IEEE Standard for Floating-Point Arithmetic",
IEEE 754-2008, DOI 10.1109/IEEESTD.2008.4610935, 2008,
<<a href="http://standards.ieee.org/findstds/standard/754-2008.html">http://standards.ieee.org/findstds/</a>
<a href="http://standards.ieee.org/findstds/standard/754-2008.html">standard/754-2008.html</a>>.
[<a id="ref-RESTCONF">RESTCONF</a>] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", Work in Progress,
<a href="./draft-ietf-netconf-restconf-16">draft-ietf-netconf-restconf-16</a>, August 2016.
[<a id="ref-RFC2315">RFC2315</a>] Kaliski, B., "PKCS #7: Cryptographic Message Syntax
Version 1.5", <a href="./rfc2315">RFC 2315</a>, DOI 10.17487/RFC2315, March 1998,
<<a href="https://www.rfc-editor.org/info/rfc2315">http://www.rfc-editor.org/info/rfc2315</a>>.
[<a id="ref-RFC6020">RFC6020</a>] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", <a href="./rfc6020">RFC 6020</a>,
DOI 10.17487/RFC6020, October 2010,
<<a href="https://www.rfc-editor.org/info/rfc6020">http://www.rfc-editor.org/info/rfc6020</a>>.
[<a id="ref-RFC7223">RFC7223</a>] Bjorklund, M., "A YANG Data Model for Interface
Management", <a href="./rfc7223">RFC 7223</a>, DOI 10.17487/RFC7223, May 2014,
<<a href="https://www.rfc-editor.org/info/rfc7223">http://www.rfc-editor.org/info/rfc7223</a>>.
[<a id="ref-RFC7515">RFC7515</a>] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", <a href="./rfc7515">RFC 7515</a>, DOI 10.17487/RFC7515, May
2015, <<a href="https://www.rfc-editor.org/info/rfc7515">http://www.rfc-editor.org/info/rfc7515</a>>.
[<a id="ref-RFC7516">RFC7516</a>] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
<a href="./rfc7516">RFC 7516</a>, DOI 10.17487/RFC7516, May 2015,
<<a href="https://www.rfc-editor.org/info/rfc7516">http://www.rfc-editor.org/info/rfc7516</a>>.
[<a id="ref-RFC7952">RFC7952</a>] Lhotka, L., "Defining and Using Metadata with YANG",
<a href="./rfc7952">RFC 7952</a>, DOI 10.17487/RFC7952, August 2016,
<<a href="https://www.rfc-editor.org/info/rfc7952">http://www.rfc-editor.org/info/rfc7952</a>>.
[<a id="ref-XML">XML</a>] 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,
<<a href="http://www.w3.org/TR/2008/REC-xml-20081126">http://www.w3.org/TR/2008/REC-xml-20081126</a>>.
<span class="grey">Lhotka Standards Track [Page 17]</span><span id="page-18" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
<span class="h2"><a class="selflink" id="appendix-A" href="#appendix-A">Appendix A</a>. A Complete Example</span>
The JSON document shown below represents the same data as the reply
to the NETCONF <get> request appearing in <a href="./rfc7223#appendix-D">Appendix D of [RFC7223]</a>.
The data model is a combination of two YANG modules:
"ietf-interfaces" and "ex-vlan" (the latter is an example module from
<a href="./rfc7223#appendix-C">Appendix C of [RFC7223]</a>). The "if-mib" feature defined in the
"ietf-interfaces" module is supported.
{
"ietf-interfaces:interfaces": {
"interface": [
{
"name": "eth0",
"type": "iana-if-type:ethernetCsmacd",
"enabled": false
},
{
"name": "eth1",
"type": "iana-if-type:ethernetCsmacd",
"enabled": true,
"ex-vlan:vlan-tagging": true
},
{
"name": "eth1.10",
"type": "iana-if-type:l2vlan",
"enabled": true,
"ex-vlan:base-interface": "eth1",
"ex-vlan:vlan-id": 10
},
{
"name": "lo1",
"type": "iana-if-type:softwareLoopback",
"enabled": true
}
]
},
"ietf-interfaces:interfaces-state": {
"interface": [
{
"name": "eth0",
"type": "iana-if-type:ethernetCsmacd",
"admin-status": "down",
"oper-status": "down",
"if-index": 2,
"phys-address": "00:01:02:03:04:05",
"statistics": {
"discontinuity-time": "2013-04-01T03:00:00+00:00"
<span class="grey">Lhotka Standards Track [Page 18]</span><span id="page-19" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
}
},
{
"name": "eth1",
"type": "iana-if-type:ethernetCsmacd",
"admin-status": "up",
"oper-status": "up",
"if-index": 7,
"phys-address": "00:01:02:03:04:06",
"higher-layer-if": [
"eth1.10"
],
"statistics": {
"discontinuity-time": "2013-04-01T03:00:00+00:00"
}
},
{
"name": "eth1.10",
"type": "iana-if-type:l2vlan",
"admin-status": "up",
"oper-status": "up",
"if-index": 9,
"lower-layer-if": [
"eth1"
],
"statistics": {
"discontinuity-time": "2013-04-01T03:00:00+00:00"
}
},
{
"name": "eth2",
"type": "iana-if-type:ethernetCsmacd",
"admin-status": "down",
"oper-status": "down",
"if-index": 8,
"phys-address": "00:01:02:03:04:07",
"statistics": {
"discontinuity-time": "2013-04-01T03:00:00+00:00"
}
},
{
"name": "lo1",
"type": "iana-if-type:softwareLoopback",
"admin-status": "up",
"oper-status": "up",
"if-index": 1,
"statistics": {
"discontinuity-time": "2013-04-01T03:00:00+00:00"
<span class="grey">Lhotka Standards Track [Page 19]</span><span id="page-20" ></span>
<span class="grey"><a href="./rfc7951">RFC 7951</a> JSON Encoding of YANG Data August 2016</span>
}
}
]
}
}
Acknowledgements
The author wishes to thank Andy Bierman, Martin Bjorklund, Dean
Bogdanovic, Balazs Lengyel, Juergen Schoenwaelder, and Phil Shafer
for their helpful comments and suggestions.
Author's Address
Ladislav Lhotka
CZ.NIC
Email: [email protected]
Lhotka Standards Track [Page 20]
Annotations
Select text to annotate