JSON Encoding of Data Modeled with YANG
draft-ietf-netmod-yang-json-04

NETMOD Working Group                                           L. Lhotka
Internet-Draft                                                    CZ.NIC
Intended status: Standards Track                           June 12, 2015
Expires: December 14, 2015

                JSON Encoding of Data Modeled with YANG
                     draft-ietf-netmod-yang-json-04

Abstract

   This document defines encoding rules for representing configuration,
   state data, RPC input and output parameters, and notifications
   defined using YANG as JavaScript Object Notation (JSON) text.

Status of This Memo

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   This Internet-Draft will expire on December 14, 2015.

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

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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   3
   3.  Validation of JSON-encoded
       Instance Data . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Names and Namespaces  . . . . . . . . . . . . . . . . . . . .   4
   5.  Encoding of YANG Data Node Instances  . . . . . . . . . . . .   6
     5.1.  The "leaf" Data Node  . . . . . . . . . . . . . . . . . .   7
     5.2.  The "container" Data Node . . . . . . . . . . . . . . . .   7
     5.3.  The "leaf-list" Data Node . . . . . . . . . . . . . . . .   7
     5.4.  The "list" Data Node  . . . . . . . . . . . . . . . . . .   8
     5.5.  The "anydata" Data Node . . . . . . . . . . . . . . . . .   9
     5.6.  The "anyxml" Data Node  . . . . . . . . . . . . . . . . .  10
   6.  The Mapping of YANG Data Types to JSON Values . . . . . . . .  10
     6.1.  Numeric Types . . . . . . . . . . . . . . . . . . . . . .  10
     6.2.  The "string" Type . . . . . . . . . . . . . . . . . . . .  11
     6.3.  The "boolean" Type  . . . . . . . . . . . . . . . . . . .  11
     6.4.  The "enumeration" Type  . . . . . . . . . . . . . . . . .  11
     6.5.  The "bits" Type . . . . . . . . . . . . . . . . . . . . .  11
     6.6.  The "binary" Type . . . . . . . . . . . . . . . . . . . .  11
     6.7.  The "leafref" Type  . . . . . . . . . . . . . . . . . . .  11
     6.8.  The "identityref" Type  . . . . . . . . . . . . . . . . .  11
     6.9.  The "empty" Type  . . . . . . . . . . . . . . . . . . . .  12
     6.10. The "union" Type  . . . . . . . . . . . . . . . . . . . .  13
     6.11. The "instance-identifier" Type  . . . . . . . . . . . . .  13
   7.  I-JSON Compliance . . . . . . . . . . . . . . . . . . . . . .  14
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     10.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Appendix A.  A Complete Example . . . . . . . . . . . . . . . . .  16
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  18
     B.1.  Changes Between Revisions -03 and -04 . . . . . . . . . .  18
     B.2.  Changes Between Revisions -02 and -03 . . . . . . . . . .  19
     B.3.  Changes Between Revisions -01 and -02 . . . . . . . . . .  19
     B.4.  Changes Between Revisions -00 and -01 . . . . . . . . . .  19
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   The NETCONF protocol [RFC6241] uses XML [W3C.REC-xml-20081126] for
   encoding data in its Content Layer.  Other management protocols might
   want to use other encodings while still benefiting from using YANG
   [I-D.ietf-netmod-rfc6020bis] as the data modeling language.

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   For example, the RESTCONF protocol [I-D.ietf-netconf-restconf]
   supports two encodings: XML (media type "application/yang.data+xml")
   and JSON (media type "application/yang.data+json).

   The specification of YANG 1.1 data modelling language
   [I-D.ietf-netmod-rfc6020bis] defines only XML encoding for data
   instances, i.e., contents of configuration datastores, state data,
   RFC input and output parameters, and event notifications.  The aim of
   this document is to define rules for encoding the same data as
   JavaScript Object Notation (JSON) text [RFC7159].

   In order to achieve maximum interoperability while allowing
   implementations to use a variety of available JSON parsers, the JSON
   encoding rules follow, as much as possible, the constraints of the
   I-JSON restricted profile [RFC7493].  Section 7 discusses I-JSON
   conformance in more detail.

2.  Terminology and Notation

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

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

   o  anydata,

   o  anyxml,

   o  augment,

   o  container,

   o  data node,

   o  identity,

   o  instance identifier,

   o  leaf,

   o  leaf-list,

   o  list,

   o  module,

   o  submodule.

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3.  Validation of JSON-encoded Instance Data

   Instance data validation as defined in [I-D.ietf-netmod-rfc6020bis],
   sec. 8.3.3, is only applicable to XML-encoded data.  For one,
   semantic constraints in "must" statements are expressed using
   XPath 1.0 [W3C.REC-xpath-19991116], which can be properly interpreted
   only in the XML context.

   This document and the corresponding "XML Mapping Rules" sections from
   [I-D.ietf-netmod-rfc6020bis] also define an implicit schema-driven
   mapping of JSON-encoded instances to XML-encoded instances (and vice
   versa).  This mapping is mostly straightforward.  In cases where
   doubts could arise, this document gives explicit instructions for
   mapping JSON-encoded instances to XML.

   In order to validate a JSON instance document, it needs first to be
   mapped, at least conceptually, to the corresponding XML instance
   document.  By definition, the JSON document is then valid if and only
   if the XML document is valid according to the rules stated in
   [I-D.ietf-netmod-rfc6020bis].

4.  Names and Namespaces

   Instances of YANG data nodes (leafs, containers, leaf-lists, lists,
   anydata and anyxml nodes) are always encoded as members of a JSON
   object, i.e., as name/value pairs.  This section defines how the name
   part is formed, and the following sections deal with the value part.

   Except in the cases specified below, the member name is identical to
   the identifier of the corresponding YANG data node.  Every such name
   belongs to a namespace which is associated with the YANG module where
   the corresponding data node is defined.  If the data node is defined
   in a submodule, then the namespace is determined by the main module
   to which the submodule belongs.

   If the namespace of a member name has to be explicitly specified, the
   module name SHALL be used as a prefix to the member's local name.
   Both parts of the member name SHALL be separated with a colon
   character (":").  Using ABNF [RFC5234], the namespace-qualified name
   can be expressed as shown in Figure 1, where the production for
   "identifier" is defined in sec. 13 of [I-D.ietf-netmod-rfc6020bis].

           qualified-member-name = identifier ":" identifier

          Figure 1: ABNF production for a qualified member name.

   Names with namespace identifiers in the form shown in Figure 1 are
   used if and only if the parent data node belongs to a different

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   namespace, which also includes all top-level YANG data nodes that
   have no parent node.

   For example, consider the following YANG module:

   module foomod {

     namespace "http://example.com/foomod";

     prefix "foo";

     container top {
       leaf foo {
         type uint8;
       }
     }
   }

   If the data model consists only of this module, then the following is
   a valid JSON-encoded configuration:

   {
     "foomod:top": {
       "foo": 54
     }
   }

   Note that the top-level container instance contains the namespace
   identifier (module name) but the "foo" leaf doesn't because it is
   defined in the same module as its parent container.

   Now, assume the container "top" is augmented from another module,
   "barmod":

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   module barmod {

     namespace "http://example.com/barmod";

     prefix "bar";

     import foomod {
       prefix "foo";
     }

     augment "/foo:top" {
       leaf bar {
         type boolean;
       }
     }
   }

   A valid JSON-encoded configuration containing both leafs may then
   look like this:

   {
     "foomod:top": {
       "foo": 54,
       "barmod:bar": true
     }
   }

   The name of the "bar" leaf is prefixed with the namespace identifier
   because its parent is defined in a different module, hence it belongs
   to another namespace.

   Explicit namespace identifiers are sometimes needed when encoding
   values of the "identityref" and "instances-identifier" types.  The
   same form as shown in Figure 1 is then used as well.  See Sections
   6.8 and 6.11 for details.

5.  Encoding of YANG Data Node Instances

   Every complete JSON instance document, such as a configuration
   datastore content, is an object.  Its members are instances of all
   top-level data nodes defined by the YANG data model.

   Character encoding MUST be UTF-8.

   Any data node instance is encoded as a name/value pair where the name
   is formed from the data node identifier using the rules of Section 4.
   The value depends on the category of the data node as explained in
   the following subsections.

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5.1.  The "leaf" Data Node

   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 Section 6 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

5.2.  The "container" Data Node

   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
   }

5.3.  The "leaf-list" Data Node

   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 Section 6 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 (sec. 7.7.7 in
   [I-D.ietf-netmod-rfc6020bis]) MUST be observed.

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   Example: For the leaf-list definition

   leaf-list foo {
     type uint8;
   }

   the following is a valid JSON-encoded instance:

   "foo": [123, 0]

5.4.  The "list" Data Node

   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 (sec. 7.7.7 in
   [I-D.ietf-netmod-rfc6020bis]) 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:

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   "bar": [
     {
       "foo": 123,
       "baz": "zig"
     },
     {
       "baz": "zag",
       "foo": 0
     }
   ]

5.5.  The "anydata" Data Node

   Anydata data node is a new feature in YANG 1.1.  It serves as a
   container for data that appear as normal YANG-modeled data, except
   their data model is not a priori known.

   An anydata instance is thus encoded in the same way as a container,
   and its content is subject to the following rules:

   o  It is a valid I-JSON message [RFC7493].

   o  Any member name is either a YANG identifier as defined by the
      "identifier" production in sec. 13 of
      [I-D.ietf-netmod-rfc6020bis], or two such identifiers separated by
      the colon character (":").  See also Section 4.

   o  Any JSON array contains either only unique scalar values (as a
      leaf-list, see Section 5.3), or only objects (as a list, see
      Section 5.4).

   o  The "null" value is only allowed in the single-element array
      "[null]" corresponding to the encoding of the "empty" type, see
      Section 6.9.

   If a data model for anydata content is not available, it may be
   impossible to map a JSON-encoded anydata instance to XML, and vice
   versa.  Note, however, that such a mapping is not needed for
   validation purposes (Section 3) because anydata contents are
   generally not subject to YANG-based validation (see sec. 7.10 in
   [I-D.ietf-netmod-rfc6020bis]).

   Example: for the anydata definition

   anydata data;

   the following is a valid JSON-encoded instance:

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   "data": {
     "ietf-notification:notification": {
       "eventTime": "2014-07-29T13:43:01Z",
       "example-event:event": {
         "event-class: "fault",
         "reporting-entity": {
           "card": "Ethernet0"
         },
         "severity": "major"
       }
     }
   }

5.6.  The "anyxml" Data Node

   An anyxml instance is encoded as a JSON name/value pair which MUST
   satisfy I-JSON constraints.  Otherwise it is unrestricted, i.e., the
   value can be an object, array, number, string or one of the literals
   "true", "false" and "null".

   As in the case of anydata (Section 5.5), there is no universal
   procedure for mapping JSON-encoded anyxml instances to XML, and vice
   versa.

   Example: For the anyxml definition

   anyxml bar;

   the following is a valid JSON-encoded instance:

   "bar": [true, null, true]

6.  The Mapping of YANG Data Types to JSON Values

   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.

6.1.  Numeric Types

   A value of the "int8", "int16", "int32", "uint8", "uint16" and
   "uint32" is represented as a JSON number.

   A value of the "int64", "uint64" or "decimal64" type is encoded as a
   JSON string whose contents is the lexical representation of that
   numeric value as specified in sections 9.2.1 and 9.3.1 of
   [I-D.ietf-netmod-rfc6020bis].

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   For example, if the type of the leaf "foo" in Section 5.1 was
   "uint64" instead of "uint8", the instance would have to be encoded as

   "foo": "123"

   The special handling of 64-bit numbers follows from I-JSON
   recommendation to encode numbers exceeding the IEEE 754-2008 double
   precision range as strings, see sec. 2.2 in [RFC7493].

6.2.  The "string" Type

   A "string" value encoded as a JSON string, subject to JSON string
   encoding rules.

6.3.  The "boolean" Type

   A "boolean" value is mapped to the corresponding JSON literal name
   "true" or "false".

6.4.  The "enumeration" Type

   An "enumeration" value is mapped in the same way as a string except
   that the permitted values are defined by "enum" statements in YANG.
   See sec. 9.6 in [I-D.ietf-netmod-rfc6020bis].

6.5.  The "bits" Type

   A "bits" value is mapped to a JSON string identical to the lexical
   representation of this value in XML, i.e., space-separated names
   representing the individual bit values that are set.  See sec. 9.7 in
   [I-D.ietf-netmod-rfc6020bis].

6.6.  The "binary" Type

   A "binary" value is mapped to a JSON string identical to the lexical
   representation of this value in XML, i.e., base64-encoded binary
   data.  See sec. 9.8 in [I-D.ietf-netmod-rfc6020bis].

6.7.  The "leafref" Type

   A "leafref" value is mapped according to the same rules as the type
   of the leaf being referred to.

6.8.  The "identityref" Type

   An "identityref" value is mapped to a string representing the name of
   an identity.  Its namespace MUST be expressed as shown in Figure 1 if

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   it is different from the namespace of the leaf node containing the
   identityref value, and MAY be expressed otherwise.

   For example, consider the following schematic module:

   module exmod {
     ...
     import ietf-interfaces {
       prefix if;
     }
     import iana-if-type {
       prefix ianaift;
     }
     ...
     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.

6.9.  The "empty" Type

   An "empty" value is mapped to "[null]", i.e., an array with the
   "null" literal being its only element.  For the purposes of this
   document, "[null]" is treated as 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.  When used in a boolean context, the "[null]"
   value, unlike "null", evaluates to true.

   Example: For the leaf definition

   leaf foo {
     type empty;
   }

   a valid instance is

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   "foo": [null]

6.10.  The "union" Type

   A value of the "union" type is encoded as the value of any of the
   member types.

   Unlike XML, JSON conveys part of the type information already in the
   encoding.  When validating a value of the "union" type, this
   information MUST also be taken into account.

   For example, consider the following YANG definition:

   leaf bar {
     type union {
       type uint16;
       type string;
     }
   }

   In RESTCONF [I-D.ietf-netconf-restconf], it is fully acceptable 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 the value is supposed to be
   a number rather than a string.

6.11.  The "instance-identifier" Type

   An "instance-identifier" value is encoded as a string that is
   analogical to the lexical representation in XML encoding, see
   sec. 9.13.3 in [I-D.ietf-netmod-rfc6020bis].  However, the encoding
   of namespaces in instance-identifier values follows the rules stated
   in Section 4, namely:

   o  The namespace identifier is the module name where each data node
      is defined.

   o  The encoding of a node name with an explicit namespace is as shown
      in Figure 1.

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   o  The leftmost (top-level) node name is always prefixed with the
      namespace identifier.

   o  Any subsequent node name has the namespace identifier if and only
      if its parent node has a different namespace.  This also holds for
      node names appearing in predicates.

   For example,

   /ietf-interfaces:interfaces/interface[name='eth0']/ietf-ip:ipv4/ip

   is a valid instance-identifer 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".

   When translating an instance-identifier value from JSON to XML, the
   namespace identifier (YANG module name) in each component of the
   instance-identifier MUST be replaced by an XML namespace prefix that
   is associated with the namespace URI reference of the module in the
   scope of the element containing the instance-identifier value.

7.  I-JSON Compliance

   I-JSON [RFC7493] 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 Section 6.1 for details.

   This document deviates from I-JSON only in the encoding of values
   with the "binary" type.  It uses the base64 encoding scheme
   (Section 6.6), whereas I-JSON recommends base64url instead.
   Theoretically, values of the "binary" type might appear in URI
   references, such as Request-URI in RESTCONF, although in practice the
   cases where it is really needed should be extremely rare.

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8.  Security Considerations

   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 sec. 16 of
   [I-D.ietf-netmod-rfc6020bis].

   JSON processing is rather different from XML, and JSON parsers may
   thus suffer from other 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 to the
   rules of this document and reply with an appropriate error message to
   the sender.

9.  Acknowledgments

   The author wishes to thank Andy Bierman, Martin Bjorklund, Dean
   Bogdanovic, Balazs Lengyel, Juergen Schoenwaelder and Phil Shafer for
   their helpful comments and suggestions.

10.  References

10.1.  Normative References

   [I-D.ietf-netmod-rfc6020bis]
              Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", draft-ietf-
              netmod-rfc6020bis-05 (work in progress), May 2015.

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

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

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

   [RFC7159]  Bray, T., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, March 2014.

   [RFC7493]  Bray, T., "The I-JSON Message Format", RFC 7493, March
              2015.

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   [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>.

10.2.  Informative References

   [I-D.ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", draft-ietf-netconf-restconf-05 (work in
              progress), June 2015.

   [RFC7223]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 7223, May 2014.

   [W3C.REC-xpath-19991116]
              Clark, J. and S. DeRose, "XML Path Language (XPath)
              Version 1.0", World Wide Web Consortium Recommendation
              REC-xpath-19991116, November 1999,
              <http://www.w3.org/TR/1999/REC-xpath-19991116>.

Appendix A.  A Complete Example

   The JSON document shown below represents the same data as the reply
   to the NETCONF <get> request appearing in Appendix D of [RFC7223].
   The data model is a combination of two YANG modules: "ietf-
   interfaces" and "ex-vlan" (the latter is an example module from
   Appendix C of [RFC7223]).  The "if-mib" feature defined in the "ietf-
   interfaces" module is considered to be active.

   {
     "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",

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           "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"
           }
         },
         {
           "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"
           ],

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           "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"
           }
         }
       ]
     }
   }

Appendix B.  Change Log

   RFC Editor: Remove this section upon publication as an RFC.

B.1.  Changes Between Revisions -03 and -04

   o  I-D.ietf-netmod-rfc6020bis is used as a normative reference
      instead of RFC 6020.

   o  Removed noncharacters as an I-JSON issue because it doesn't exist
      in YANG 1.1.

   o  Section about anydata encoding was added.

   o  Require I-JSON for anyxml encoding.

   o  Use ABNF for defining qualified name.

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B.2.  Changes Between Revisions -02 and -03

   o  Namespace encoding is defined without using RFC 2119 keywords.

   o  Specification for anyxml nodes was extended and clarified.

   o  Text about ordering of list entries was corrected.

B.3.  Changes Between Revisions -01 and -02

   o  Encoding of namespaces in instance-identifiers was changed.

   o  Text specifying the order of array elements in leaf-list and list
      instances was added.

B.4.  Changes Between Revisions -00 and -01

   o  Metadata encoding was moved to a separate I-D, draft-lhotka-
      netmod-yang-metadata.

   o  JSON encoding is now defined directly rather than via XML-JSON
      mapping.

   o  The rules for namespace encoding has changed.  This affect both
      node instance names and instance-identifiers.

   o  I-JSON-related changes.  The most significant is the string
      encoding of 64-bit numbers.

   o  When validating union type, the partial type info present in JSON
      encoding is taken into account.

   o  Added section about I-JSON compliance.

   o  Updated the example in appendix.

   o  Wrote Security Considerations.

   o  Removed IANA Considerations as there are none.

Author's Address

   Ladislav Lhotka
   CZ.NIC

   Email: lhotka@nic.cz

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