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Versions: (draft-veillette-core-yang-cbor-mapping) 00 01 02 03 04 05 06 07 08 09 10

Internet Engineering Task Force                        M. Veillette, Ed.
Internet-Draft                                   Trilliant Networks Inc.
Intended status: Standards Track                          I. Petrov, Ed.
Expires: October 4, 2019                                        A. Pelov
                                                                  Acklio
                                                          April 02, 2019


                CBOR Encoding of Data Modeled with YANG
                      draft-ietf-core-yang-cbor-09

Abstract

   This document defines encoding rules for serializing configuration
   data, state data, RPC input and RPC output, Action input, Action
   output and notifications defined within YANG modules using the
   Concise Binary Object Representation (CBOR) [RFC7049].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 4, 2019.

Copyright Notice

   Copyright (c) 2019 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   3
   3.  Properties of the CBOR Encoding . . . . . . . . . . . . . . .   4
     3.1.  CBOR diagnostic notation  . . . . . . . . . . . . . . . .   5
     3.2.  YANG Schema Item iDentifier (SID) . . . . . . . . . . . .   6
     3.3.  Name  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Encoding of YANG Schema Node Instances  . . . . . . . . . . .   9
     4.1.  The 'leaf'  . . . . . . . . . . . . . . . . . . . . . . .   9
     4.2.  The 'container' and other collections . . . . . . . . . .   9
       4.2.1.  SIDs as keys  . . . . . . . . . . . . . . . . . . . .  10
       4.2.2.  Names as keys . . . . . . . . . . . . . . . . . . . .  11
     4.3.  The 'leaf-list' . . . . . . . . . . . . . . . . . . . . .  13
     4.4.  The 'list' and 'list' instance(s) . . . . . . . . . . . .  14
       4.4.1.  SIDs as keys  . . . . . . . . . . . . . . . . . . . .  15
       4.4.2.  Names as keys . . . . . . . . . . . . . . . . . . . .  17
     4.5.  The 'anydata' . . . . . . . . . . . . . . . . . . . . . .  19
     4.6.  The 'anyxml'  . . . . . . . . . . . . . . . . . . . . . .  21
   5.  Encoding of YANG data templates . . . . . . . . . . . . . . .  22
     5.1.  SIDs as keys  . . . . . . . . . . . . . . . . . . . . . .  23
     5.2.  Names as keys . . . . . . . . . . . . . . . . . . . . . .  24
   6.  Representing YANG Data Types in CBOR  . . . . . . . . . . . .  25
     6.1.  The unsigned integer Types  . . . . . . . . . . . . . . .  25
     6.2.  The integer Types . . . . . . . . . . . . . . . . . . . .  26
     6.3.  The 'decimal64' Type  . . . . . . . . . . . . . . . . . .  26
     6.4.  The 'string' Type . . . . . . . . . . . . . . . . . . . .  27
     6.5.  The 'boolean' Type  . . . . . . . . . . . . . . . . . . .  27
     6.6.  The 'enumeration' Type  . . . . . . . . . . . . . . . . .  27
     6.7.  The 'bits' Type . . . . . . . . . . . . . . . . . . . . .  28
     6.8.  The 'binary' Type . . . . . . . . . . . . . . . . . . . .  30
     6.9.  The 'leafref' Type  . . . . . . . . . . . . . . . . . . .  30
     6.10. The 'identityref' Type  . . . . . . . . . . . . . . . . .  31
       6.10.1.  SIDs as identityref  . . . . . . . . . . . . . . . .  31
       6.10.2.  Name as identityref  . . . . . . . . . . . . . . . .  32
     6.11. The 'empty' Type  . . . . . . . . . . . . . . . . . . . .  32
     6.12. The 'union' Type  . . . . . . . . . . . . . . . . . . . .  33
     6.13. The 'instance-identifier' Type  . . . . . . . . . . . . .  34
       6.13.1.  SIDs as instance-identifier  . . . . . . . . . . . .  34
       6.13.2.  Names as instance-identifier . . . . . . . . . . . .  37
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  39
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  39
     8.1.  Tags Registry . . . . . . . . . . . . . . . . . . . . . .  39
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  39
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  40



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     10.1.  Normative References . . . . . . . . . . . . . . . . . .  40
     10.2.  Informative References . . . . . . . . . . . . . . . . .  40
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  41

1.  Introduction

   The specification of the YANG 1.1 data modelling language [RFC7950]
   defines an XML encoding for data instances, i.e. contents of
   configuration datastores, state data, RPC inputs and outputs, action
   inputs and outputs, and event notifications.

   A new set of encoding rules has been defined to allow the use of the
   same data models in environments based on the JavaScript Object
   Notation (JSON) Data Interchange Format [RFC7159].  This is
   accomplished in the JSON Encoding of Data Modeled with YANG
   specification [RFC7951].

   The aim of this document is to define a set of encoding rules for the
   Concise Binary Object Representation (CBOR) [RFC7049].  The resulting
   encoding is more compact compared to XML and JSON and more suitable
   for Constrained Nodes and/or Constrained Networks as defined by
   [RFC7228].

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 [RFC7950]:

   o  action

   o  anydata

   o  anyxml

   o  data node

   o  data tree

   o  datastore

   o  feature

   o  identity

   o  module



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   o  notification

   o  RPC

   o  schema node

   o  schema tree

   o  submodule

   The following terms are defined in [RFC8040]:

   o  yang-data (YANG extension)

   o  YANG data template

   This specification also makes use of the following terminology:

   o  child: A schema node defined within a collection such as a
      container, a list, a case, a notification, an RPC input, an RPC
      output, an action input, an action output.

   o  delta: Difference between the current SID and a reference SID.  A
      reference SID is defined for each context for which deltas are
      used.

   o  item: A schema node, an identity, a module, a submodule or a
      feature defined using the YANG modeling language.

   o  parent: The collection in which a schema node is defined.

   o  YANG Schema Item iDentifier (SID): Unsigned integer used to
      identify different YANG items.

3.  Properties of the CBOR Encoding

   This document defines CBOR encoding rules for YANG schema trees and
   their subtrees.

   A collection such as container, list instance, notification, RPC
   input, RPC output, action input and action output is serialized using
   a CBOR map in which each child schema node is encoded using a key and
   a value.  This specification supports two type of CBOR keys; YANG
   Schema Item iDentifier (SID) as defined in Section 3.2 and names as
   defined in Section 3.3.  Each of these key types is encoded using a
   specific CBOR type which allows their interpretation during the
   deserialization process.  Protocols or mechanisms implementing this
   specification can mandate the use of a specific key type.



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   In order to minimize the size of the encoded data, the proposed
   mapping avoids any unnecessary meta-information beyond those natively
   supported by CBOR.  For instance, CBOR tags are used solely in the
   case of anyxml schema nodes and the union datatype to distinguish
   explicitly the use of different YANG datatypes encoded using the same
   CBOR major type.

   Unless specified otherwise by the protocol or mechanism implementing
   this specification, the infinite lengths encoding as defined in
   [RFC7049] section 2.2 SHALL be supported by CBOR decoders.

   Data nodes implemented using a CBOR array, map, byte string, and text
   string can be instantiated but empty.  In this case, they are encoded
   with a length of zero.

   Application payloads carrying a value serialized using the rules
   defined by this specification (e.g.  CoAP Content-Format) SHOULD
   include the identifier (e.g.  SID, namespace qualified name,
   instance-identifier) of this value.  When SIDs are used as
   identifiers, the reference SID SHALL be included in the payload to
   allow stateless conversion of delta values to SIDs.  Formats of these
   application payloads are not defined by the current specification.

3.1.  CBOR diagnostic notation

   Within this document, CBOR binary contents are represented using an
   equivalent textual form called CBOR diagnostic notation as defined in
   [RFC7049] section 6.  This notation is used strictly for
   documentation purposes and is never used in the data serialization.
   Table 1 below provides a summary of this notation.





















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   +----------+------+--------------------------+-----------+----------+
   | CBOR     | CBOR | Diagnostic notation      | Example   | CBOR     |
   | content  | type |                          |           | encoding |
   +----------+------+--------------------------+-----------+----------+
   | Unsigned | 0    | Decimal digits           | 123       | 18 7B    |
   | integer  |      |                          |           |          |
   | Negative | 1    | Decimal digits prefixed  | -123      | 38 7A    |
   | integer  |      | by a minus sign          |           |          |
   | Byte     | 2    | Hexadecimal value        | h'F15C'   | 42 f15C  |
   | string   |      | enclosed between single  |           |          |
   |          |      | quotes and prefixed by   |           |          |
   |          |      | an 'h'                   |           |          |
   | Text     | 3    | String of Unicode        | "txt"     | 63       |
   | string   |      | characters enclosed      |           | 747874   |
   |          |      | between double quotes    |           |          |
   | Array    | 4    | Comma-separated list of  | [ 1, 2 ]  | 82 01 02 |
   |          |      | values within square     |           |          |
   |          |      | brackets                 |           |          |
   | Map      | 5    | Comma-separated list of  | { 1: 123, | a2       |
   |          |      | key : value pairs within | 2: 456 }  | 01187B   |
   |          |      | curly braces             |           | 021901C8 |
   | Boolean  | 7/20 | false                    | false     | F4       |
   |          | 7/21 | true                     | true      | F5       |
   | Null     | 7/22 | null                     | null      | F6       |
   | Not      | 7/23 | undefined                | undefined | F7       |
   | assigned |      |                          |           |          |
   +----------+------+--------------------------+-----------+----------+

                 Table 1: CBOR diagnostic notation summary

   The following extensions to the CBOR diagnostic notation are
   supported:

   o  Any text within and including a pair of slashes is considered a
      comment.

   o  Deltas are visualized as numbers preceded by a '+' or '-' sign.
      The use of the '+' sign for positive deltas represents an
      extension to the CBOR diagnostic notation as defined by [RFC7049]
      section 6.

3.2.  YANG Schema Item iDentifier (SID)

   Some of the items defined in YANG [RFC7950] require the use of a
   unique identifier.  In both NETCONF [RFC6241] and RESTCONF [RFC8040],
   these identifiers are implemented using strings.  To allow the
   implementation of data models defined in YANG in constrained devices
   and constrained networks, a more compact method to identify YANG



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   items is required.  This compact identifier, called YANG Schema Item
   iDentifier (SID), is an unsigned integer.  The following items are
   identified using SIDs:

   o  identities

   o  data nodes

   o  RPCs and associated input(s) and output(s)

   o  actions and associated input(s) and output(s)

   o  notifications and associated information

   o  YANG modules, submodules and features

   To minimize its size, in certain positions, SIDs are represented
   using a (signed) delta from a reference SID and the current SID.
   Conversion from SIDs to deltas and back to SIDs are stateless
   processes solely based on the data serialized or deserialized.

   Mechanisms and processes used to assign SIDs to YANG items and to
   guarantee their uniqueness is outside the scope of the present
   specification.  If SIDs are to be used, the present specification is
   used in conjunction with a specification defining this management.
   One example for such a specification is under development as
   [I-D.ietf-core-sid].

3.3.  Name

   This specification also supports the encoding of YANG item
   identifiers as string, similar as those used by the JSON Encoding of
   Data Modeled with YANG [RFC7951].  This approach can be used to avoid
   the management overhead associated to SIDs allocation.  The main
   drawback is the significant increase is size of the encoded data.

   YANG items identifiers implemented using names MUST be in one of the
   following forms:

   o  simple - the identifier of the YANG item (i.e. schema node or
      identity).

   o  namespace qualified - the identifier of the YANG item is prefixed
      with the name of the module in which this item is defined,
      separated by the colon character (":").

   The name of a module determines the namespace of all YANG items
   defined in that module.  If an item is defined in a submodule, then



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   the namespace qualified name uses the name of the main module to
   which the submodule belongs.

   ABNF syntax [RFC5234] of a name is shown in Figure 1, where the
   production for "identifier" is defined in Section 14 of [RFC7950].

                    name = [identifier ":"] identifier

    Figure 1: ABNF Production for a simple or namespace qualified name

   A namespace qualified name MUST be used for all members of a top-
   level CBOR map 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 name SHOULD be used.

   Definition example:

   module example-foomod {
     container top {
       leaf foo {
         type uint8;
       }
     }
   }

   module example-barmod {
     import example-foomod {
       prefix "foomod";
     }
     augment "/foomod:top" {
       leaf bar {
         type boolean;
       }
     }
   }

   A valid CBOR encoding of the 'top' container is as follow.

   CBOR diagnostic notation:

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





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   Both the 'top' container and the 'bar' leaf defined in a different
   YANG module as its parent container are encoded as namespace
   qualified names.  The 'foo' leaf defined in the same YANG module as
   its parent container is encoded as simple name.

4.  Encoding of YANG Schema Node Instances

   Schema node instances defined using the YANG modeling language are
   encoded using CBOR [RFC7049] based on the rules defined in this
   section.  We assume that the reader is already familiar with both
   YANG [RFC7950] and CBOR [RFC7049].

4.1.  The 'leaf'

   A 'leaf' MUST be encoded accordingly to its datatype using one of the
   encoding rules specified in Section 6.

4.2.  The 'container' and other collections

   Collections such as containers, list instances, notification
   contents, rpc inputs, rpc outputs, action inputs and action outputs
   MUST be encoded using a CBOR map data item (major type 5).  A map is
   comprised of pairs of data items, with each data item consisting of a
   key and a value.  Each key within the CBOR map is set to a schema
   node identifier, each value is set to the value of this schema node
   instance according to the instance datatype.

   This specification supports two type of CBOR keys; SID as defined in
   Section 3.2 and names as defined in Section 3.3.

   The following examples shows the encoding of a 'system-state'
   container instance using SIDs or names.

   Definition example from [RFC7317]:

















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   typedef date-and-time {
     type string {
       pattern '\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?(Z|[\+\-]
                \d{2}:\d{2})';
     }
   }

   container system-state {

     container clock {
       leaf current-datetime {
         type date-and-time;
       }

       leaf boot-datetime {
         type date-and-time;
       }
     }
   }

4.2.1.  SIDs as keys

   CBOR map keys implemented using SIDs MUST be encoded using a CBOR
   unsigned integer (major type 0) or CBOR negative integer (major type
   1), depending on the actual delta or to a SID preceded by the CBOR
   tag 99.

   // RFC Ed.: replace 99 by the allocated CBOR tag.

   Delta values are computed as follows:

   o  In the case of a 'container', deltas are equal to the SID of the
      current schema node minus the SID of the parent 'container'.

   o  In the case of a 'list', deltas are equal to the SID of the
      current schema node minus the SID of the parent 'list'.

   o  In the case of an 'rpc input' or 'rcp output', deltas are equal to
      the SID of the current schema node minus the SID of the 'rpc'.

   o  In the case of an 'action input' or 'action output', deltas are
      equal to the SID of the current schema node minus the SID of the
      'action'.

   o  In the case of an 'notification content', deltas are equal to the
      SID of the current schema node minus the SID of the
      'notification'.




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   This example assumes that the Media Type used to carry this container
   consists of a CBOR map composed of the data node SID and data node
   encoding.  This root CBOR map is not part of the present encoding
   rules and is not compulsory.

   CBOR diagnostic notation:

 {
   1720 : {                              / system-state /
     +1 : {                              / clock  (SID 1721) /
       +2 : "2015-10-02T14:47:24Z-05:00",/ current-datetime (SID 1723) /
       +1 : "2015-09-15T09:12:58Z-05:00" / boot-datetime (SID 1722) /
     }
   }
 }

   CBOR encoding:

   A1                                      # map(1)
      19 06B8                              # unsigned(1720)
      A1                                   # map(1)
         01                                # unsigned(1)
         A2                                # map(2)
            02                             # unsigned(2)
            78 1A                          # text(26)
               323031352D31302D30325431343A34373A32345A2D30353A3030
            01                             # unsigned(1)
            78 1A                          # text(26)
               323031352D30392D31355430393A31323A35385A2D30353A3030

4.2.2.  Names as keys

   CBOR map keys implemented using names MUST be encoded using a CBOR
   text string data item (major type 3).  A namespace-qualified name
   MUST be used each time the namespace of a schema node and its parent
   differ.  In all other cases, the simple form of the name MUST be
   used.  Names and namespaces are defined in [RFC7951] section 4.

   The following example shows the encoding of a 'system' container
   instance using names.

   Definition example from [RFC7317]:









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   typedef date-and-time {
     type string {
       pattern '\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?(Z|[\+\-]
                \d{2}:\d{2})';
     }
   }

   container system-state {

     container clock {
       leaf current-datetime {
         type date-and-time;
       }

       leaf boot-datetime {
         type date-and-time;
       }
     }
   }

   This example assumes that the Media Type used to carry this container
   consists of a CBOR map composed of the data node namespace qualified
   name and data node encoding.  This root CBOR map is not part of the
   present encoding rules and is not compulsory.

   CBOR diagnostic notation:

   {
     "ietf-system:system-state" : {
       "ietf-system:clock" : {
         "current-datetime" : "2015-10-02T14:47:24Z-05:00",
         "boot-datetime" : "2015-09-15T09:12:58Z-05:00"
       }
     }
   }

   CBOR encoding:














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   A1                                      # map(1)
      78 18                                # text(24)
         696574662D73797374656D3A73797374656D2D7374617465
      A1                                   # map(1)
         71                                # text(17)
            696574662D73797374656D3A636C6F636B
         A2                                # map(2)
            70                             # text(16)
               63757272656E742D6461746574696D65
            78 1A                          # text(26)
               323031352D31302D30325431343A34373A32345A2D30353A3030
            6D                             # text(13)
               626F6F742D6461746574696D65
            78 1A                          # text(26)
               323031352D30392D31355430393A31323A35385A2D30353A3030

4.3.  The 'leaf-list'

   A leaf-list MUST be encoded using a CBOR array data item (major type
   4).  Each entry of this array MUST be encoded accordingly to its
   datatype using one of the encoding rules specified in Section 6.

   The following example shows the encoding of the 'search' leaf-list
   instance containing two entries, "ietf.org" and "ieee.org".

   Definition example [RFC7317]:

   typedef domain-name {
     type string {
       length "1..253";
       pattern '((([a-zA-Z0-9_]([a-zA-Z0-9\-_]){0,61})?[a-zA-Z0-9].)
                *([a-zA-Z0-9_]([a-zA-Z0-9\-_]){0,61})?[a-zA-Z0-9]\.?
                )|\.';
     }
   }

   leaf-list search {
     type domain-name;
     ordered-by user;
   }

   CBOR diagnostic notation: [ "ietf.org", "ieee.org" ]

   CBOR encoding: 82 68 696574662E6F7267 68 696565652E6F7267







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4.4.  The 'list' and 'list' instance(s)

   A list or a subset of a list MUST be encoded using a CBOR array data
   item (major type 4).  Each list instance within this CBOR array is
   encoded using a CBOR map data item (major type 5) based on the
   encoding rules of a collection as defined in Section 4.2.

   It is important to note that this encoding rule also apply to a
   single 'list' instance.

   The following examples show the encoding of a 'server' list using
   SIDs or names.

   Definition example from [RFC7317]:





































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   list server {
     key name;

     leaf name {
       type string;
     }
     choice transport {
       case udp {
         container udp {
           leaf address {
             type host;
             mandatory true;
           }
           leaf port {
             type port-number;
           }
         }
       }
     }
     leaf association-type {
       type enumeration {
         enum server;
         enum peer;
         enum pool;
       }
       default server;
     }
     leaf iburst {
       type boolean;
       default false;
     }
     leaf prefer {
       type boolean;
       default false;
     }
   }

4.4.1.  SIDs as keys

   The encoding rules of each 'list' instance are defined in
   Section 4.2.1.  Deltas of list members are equal to the SID of the
   current schema node minus the SID of the 'list'.

   This example assumes that the Media Type used to carry this list
   consists of a CBOR map composed of the data node SID and data node
   encoding.  This root CBOR map is not part of the present encoding
   rules and is not compulsory.




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   CBOR diagnostic notation:

   {
     1756 : [                      / server (SID 1756) /
       {
         +3 : "NRC TIC server",    / name (SID 1759) /
         +5 : {                    / udp (SID 1761) /
           +1 : "tic.nrc.ca",      / address (SID 1762) /
           +2 : 123                / port (SID 1763) /
         },
         +1 : 0,                   / association-type (SID 1757) /
         +2 : false,               / iburst (SID 1758) /
         +4 : true                 / prefer (SID 1760) /
       },
       {
         +3 : "NRC TAC server",    / name (SID 1759) /
         +5 : {                    / udp (SID 1761) /
           +1 : "tac.nrc.ca"       / address (SID 1762) /
         }
       }
     ]
   }

   CBOR encoding:



























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   A1                                      # map(1)
      19 06DC                              # unsigned(1756)
      82                                   # array(2)
         A5                                # map(5)
            03                             # unsigned(3)
            6E                             # text(14)
               4E52432054494320736572766572 # "NRC TIC server"
            05                             # unsigned(5)
            A2                             # map(2)
               01                          # unsigned(1)
               6A                          # text(10)
                  7469632E6E72632E6361     # "tic.nrc.ca"
               02                          # unsigned(2)
               18 7B                       # unsigned(123)
            01                             # unsigned(1)
            00                             # unsigned(0)
            02                             # unsigned(2)
            F4                             # primitive(20)
            04                             # unsigned(4)
            F5                             # primitive(21)
         A2                                # map(2)
            03                             # unsigned(3)
            6E                             # text(14)
               4E52432054414320736572766572 # "NRC TAC server"
            05                             # unsigned(5)
            A1                             # map(1)
               01                          # unsigned(1)
               6A                          # text(10)
                  7461632E6E72632E6361     # "tac.nrc.ca"

4.4.2.  Names as keys

   The encoding rules of each 'list' instance are defined in
   Section 4.2.2.

   This example assumes that the Media Type used to carry this container
   consists of a CBOR map composed of the data node namespace qualified
   name and data node encoding.  This root CBOR map is not part of the
   present encoding rules and is not compulsory.

   CBOR diagnostic notation:










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   {
     "ietf-system:server" : [
       {
         "name" : "NRC TIC server",
         "udp" : {
           "address" : "tic.nrc.ca",
           "port" : 123
         },
         "association-type" : 0,
         "iburst" : false,
         "prefer" : true
       },
       {
         "name" : "NRC TAC server",
         "udp" : {
           "address" : "tac.nrc.ca"
         }
       }
     ]
   }

   CBOR encoding:





























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   A1                                      # map(1)
      72                                   # text(18)
         696574662D73797374656D3A736572766572
      82                                   # array(2)
         A5                                # map(5)
            64                             # text(4)
               6E616D65                    # "name"
            6E                             # text(14)
               4E52432054494320736572766572
            63                             # text(3)
               756470                      # "udp"
            A2                             # map(2)
               67                          # text(7)
                  61646472657373           # "address"
               6A                          # text(10)
                  7469632E6E72632E6361     # "tic.nrc.ca"
               64                          # text(4)
                  706F7274                 # "port"
               18 7B                       # unsigned(123)
            70                             # text(16)
               6173736F63696174696F6E2D74797065
            00                             # unsigned(0)
            66                             # text(6)
               696275727374                # "iburst"
            F4                             # primitive(20)
            66                             # text(6)
               707265666572                # "prefer"
            F5                             # primitive(21)
         A2                                # map(2)
            64                             # text(4)
               6E616D65                    # "name"
            6E                             # text(14)
               4E52432054414320736572766572
            63                             # text(3)
               756470                      # "udp"
            A1                             # map(1)
               67                          # text(7)
                  61646472657373           # "address"
               6A                          # text(10)
                  7461632E6E72632E6361     # "tac.nrc.ca"

4.5.  The 'anydata'

   An anydata serves as a container for an arbitrary set of schema nodes
   that otherwise appear as normal YANG-modeled data.  An anydata
   instance is encoded using the same rules as a container, i.e., CBOR
   map.  The requirement that anydata content can be modeled by YANG
   implies the following:



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   o  CBOR map keys of any inner schema nodes MUST be set to valid
      deltas or names.

   o  The CBOR array MUST contain either unique scalar values (as a
      leaf-list, see Section 4.3), or maps (as a list, see Section 4.4).

   o  CBOR map values MUST follow the encoding rules of one of the
      datatypes listed in Section 4.

   The following example shows a possible use of an anydata.  In this
   example, an anydata is used to define a schema node containing a
   notification event, this schema node can be part of a YANG list to
   create an event logger.

   Definition example:

   module event-log {
     ...
     anydata last-event;                # SID 60123

   This example also assumes the assistance of the following
   notification.

   module example-port {
     ...

     notification example-port-fault {  # SID 60200
       leaf port-name {                 # SID 60201
         type string;
       }
       leaf port-fault {                # SID 60202
         type string;
       }
     }
   }

   This example assumes that the Media Type used to carry this anydata
   consists of a CBOR map composed of the data node SID and data node
   encoding.  This root CBOR map is not part of the present encoding
   rules and is not compulsory.

   CBOR diagnostic notation:









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   {
     60123 : {                   / last-event (SID=60123) /
       +77 : {                   / event (SID=60200) /
         +1 : "0/4/21",          / port-name (SID=60201) /
         +2 : "Open pin 2"       / port-fault (SID=60202) /
       }
     }
   }

   CBOR encoding:

   A1                               # map(1)
      19 EADB                       # unsigned(60123)
      A1                            # map(1)
         18 4D                      # unsigned(77)
         A2                         # map(2)
            18 4E                   # unsigned(78)
            66                      # text(6)
               302F342F3231         # "0/4/21"
            18 4F                   # unsigned(79)
            6A                      # text(10)
               4F70656E2070696E2032 # "Open pin 2"


   In some implementations, it might be simpler to use the absolute SID
   tag encoding for the anydata root element.  The resulting encoding is
   as follow:

   {
     60123 : {                   / last-event (SID=60123) /
       99(60200) : {             / event (SID=60123) /
         +1 : "0/4/21",          / port-name (SID=60201) /
         +2 : "Open pin 2"       / port-fault (SID=60202) /
       }
     }
   }

   // RFC Ed.: replace 99 by the allocated CBOR tag.

4.6.  The 'anyxml'

   An anyxml schema node is used to serialize an arbitrary CBOR content,
   i.e., its value can be any CBOR binary object. anyxml value MAY
   contain CBOR data items tagged with one of the tag listed in
   Section 8.1, these tags shall be supported.






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   The following example shows a valid CBOR encoded instance consisting
   of a CBOR array containing the CBOR simple values 'true', 'null' and
   'true'.

   Definition example from [RFC7951]:

   anyxml bar;

   Note: This example assumes that the Media Type used to carry this
   anyxml consists of a CBOR map composed of the data node SID and data
   node encoding.  This root CBOR map is not part of the present
   encoding rules and is not compulsory.

   CBOR diagnostic notation:

   {
     60000 : [true, null, true]   / bar (SID 60000) /
   }

   CBOR encoding:

   A1         # map(1)
      19 EA60 # unsigned(60000)
      83      # array(3)
         F5   # primitive(21)
         F6   # primitive(22)
         F5   # primitive(21)

5.  Encoding of YANG data templates

   YANG data templates are data structures defined in YANG but not
   intended to be implemented as part of a datastore.  YANG data
   templates are defined using the 'yang-data' extension as described by
   RFC 8040.

   YANG data templates SHOULD be encoded using the encoding rules of a
   collection as defined in Section 4.2.

   Just like YANG containers, YANG data templates can be encoded using
   either SIDs or names.

   Definition example from [I-D.ietf-core-comi]:









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   import ietf-restconf {
     prefix rc;
   }

   rc:yang-data yang-errors {
     container error {
       leaf error-tag {
         type identityref {
           base error-tag;
         }
       }
       leaf error-app-tag {
         type identityref {
           base error-app-tag;
         }
       }
       leaf error-data-node {
         type instance-identifier;
       }
       leaf error-message {
         type string;
       }
     }
   }

5.1.  SIDs as keys

   YANG template encoded using SIDs are carried in a CBOR map containing
   a single item pair.  The key of this item is set to the SID assigned
   to the YANG template container, the value is set the CBOR encoding of
   this container as defined in Section 4.2.

   This example shows a serialization example of the yang-errors
   template as defined in [I-D.ietf-core-comi] using SIDs as defined in
   Section 3.2.

   CBOR diagnostic notation:














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   {
     1024 : {                      / error  (SID 1024) /
       +4 : 1011,                  / error-tag (SID 1028) /
                                   / = invalid-value (SID 1011) /
       +1 : 1018,                  / error-app-tag (SID 1025) /
                                   / = not-in-range (SID 1018) /
       +2 : 1740,                  / error-data-node (SID 1026) /
                                   / = timezone-utc-offset (SID 1740) /
       +3 : "Maximum exceeded"     / error-message (SID 1027) /
         }
   }

   CBOR encoding:

   A1                                      # map(1)
      19 0400                              # unsigned(1024)
      A4                                   # map(4)
         04                                # unsigned(4)
         19 03F3                           # unsigned(1011)
         01                                # unsigned(1)
         19 03FA                           # unsigned(1018)
         02                                # unsigned(2)
         19 06CC                           # unsigned(1740)
         03                                # unsigned(3)
         70                                # text(16)
            4D6178696D756D206578636565646564

5.2.  Names as keys

   YANG template encoded using names are carried in a CBOR map
   containing a single item pair.  The key of this item is set to the
   namespace qualified name of the YANG template container, the value is
   set the CBOR encoding of this container as defined in Section 3.3.

   This example shows a serialization example of the yang-errors
   template as defined in [I-D.ietf-core-comi] using names as defined
   Section 3.3.

   CBOR diagnostic notation:

   {
     "ietf-comi:error" : {
       "error-tag" : "invalid-value",
       "error-app-tag" : "not-in-range",
       "error-data-node" : "timezone-utc-offset",
       "error-message" : "Maximum exceeded"
     }
   }



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   CBOR encoding:

 A1                                      # map(1)
    6F                                   # text(15)
       696574662D636F6D693A6572726F72    # "ietf-comi:error"
    A4                                   # map(4)
       69                                # text(9)
          6572726F722D746167             # "error-tag"
       6D                                # text(13)
          696E76616C69642D76616C7565     # "invalid-value"
       6D                                # text(13)
          6572726F722D6170702D746167     # "error-app-tag"
       6C                                # text(12)
          6E6F742D696E2D72616E6765       # "not-in-range"
       6F                                # text(15)
          6572726F722D646174612D6E6F6465 # "error-data-node"
       73                                # text(19)
          74696D657A6F6E652D7574632D6F6666736574 # "timezone-utc-offset"
       6D                                # text(13)
          6572726F722D6D657373616765     # "error-message"
       70                                # text(16)
          4D6178696D756D206578636565646564

6.  Representing YANG Data Types in CBOR

   The CBOR encoding of an instance of a leaf or leaf-list schema node
   depends on the built-in type of that schema node.  The following sub-
   section defined the CBOR encoding of each built-in type supported by
   YANG as listed in [RFC7950] section 4.2.4.  Each subsection shows an
   example value assigned to a schema node instance of the discussed
   built-in type.

6.1.  The unsigned integer Types

   Leafs of type uint8, uint16, uint32 and uint64 MUST be encoded using
   a CBOR unsigned integer data item (major type 0).

   The following example shows the encoding of a 'mtu' leaf instance set
   to 1280 bytes.

   Definition example from [RFC7277]:

   leaf mtu {
     type uint16 {
       range "68..max";
     }
   }




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   CBOR diagnostic notation: 1280

   CBOR encoding: 19 0500

6.2.  The integer Types

   Leafs of type int8, int16, int32 and int64 MUST be encoded using
   either CBOR unsigned integer (major type 0) or CBOR negative integer
   (major type 1), depending on the actual value.

   The following example shows the encoding of a 'timezone-utc-offset'
   leaf instance set to -300 minutes.

   Definition example from [RFC7317]:

   leaf timezone-utc-offset {
     type int16 {
       range "-1500 .. 1500";
     }
   }

   CBOR diagnostic notation: -300

   CBOR encoding: 39 012B

6.3.  The 'decimal64' Type

   Leafs of type decimal64 MUST be encoded using a decimal fraction as
   defined in [RFC7049] section 2.4.3.

   The following example shows the encoding of a 'my-decimal' leaf
   instance set to 2.57.

   Definition example from [RFC7317]:

   leaf my-decimal {
     type decimal64 {
       fraction-digits 2;
       range "1 .. 3.14 | 10 | 20..max";
     }
   }

   CBOR diagnostic notation: 4([-2, 257])

   CBOR encoding: C4 82 21 19 0101






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6.4.  The 'string' Type

   Leafs of type string MUST be encoded using a CBOR text string data
   item (major type 3).

   The following example shows the encoding of a 'name' leaf instance
   set to "eth0".

   Definition example from [RFC7223]:

   leaf name {
     type string;
   }

   CBOR diagnostic notation: "eth0"

   CBOR encoding: 64 65746830

6.5.  The 'boolean' Type

   Leafs of type boolean MUST be encoded using a CBOR simple value
   'true' (major type 7, additional information 21) or 'false' (major
   type 7, additional information 20).

   The following example shows the encoding of an 'enabled' leaf
   instance set to 'true'.

   Definition example from [RFC7317]:

   leaf enabled {
     type boolean;
   }

   CBOR diagnostic notation: true

   CBOR encoding: F5

6.6.  The 'enumeration' Type

   Leafs of type enumeration MUST be encoded using a CBOR unsigned
   integer (major type 0) or CBOR negative integer (major type 1),
   depending on the actual value.  Enumeration values are either
   explicitly assigned using the YANG statement 'value' or automatically
   assigned based on the algorithm defined in [RFC7950] section 9.6.4.2.

   The following example shows the encoding of an 'oper-status' leaf
   instance set to 'testing'.




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   Definition example from [RFC7317]:

   leaf oper-status {
     type enumeration {
       enum up { value 1; }
       enum down { value 2; }
       enum testing { value 3; }
       enum unknown { value 4; }
       enum dormant { value 5; }
       enum not-present { value 6; }
       enum lower-layer-down { value 7; }
     }
   }

   CBOR diagnostic notation: 3

   CBOR encoding: 03

   To avoid overlap of 'value' defined in different 'enumeration'
   statements, 'enumeration' defined in a Leafs of type 'union' MUST be
   encoded using a CBOR text string data item (major type 3) and MUST
   contain one of the names assigned by 'enum' statements in YANG.  The
   encoding MUST be prefixed with the enumeration CBOR tag as specified
   in Section 8.1.

   Definition example from [RFC7950]:

   type union {
     type int32;
     type enumeration {
       enum "unbounded";
     }
   }

   CBOR diagnostic notation: 99("unbounded")

   CBOR encoding: D8 63 69 756E626F756E646564

   // RFC Ed.: update 99 and D8 63 with the enumerator CBOR tag
   allocated.

6.7.  The 'bits' Type

   Leafs of type bits MUST be encoded using a CBOR byte string data item
   (major type 2).  Bits position are either explicitly assigned using
   the YANG statement 'position' or automatically assigned based on the
   algorithm defined in [RFC7950] section 9.7.4.2.




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   Bits position 0 to 7 are assigned to the first byte within the byte
   string, bits 8 to 15 to the second byte, and subsequent bytes are
   assigned similarly.  Within each byte, bits are assigned from least
   to most significant.

   The following example shows the encoding of an 'alarm-state' leaf
   instance with the 'under-repair' and 'critical' flags set.

   Definition example from [RFC8348]:

   typedef alarm-state {
     type bits {
       bit unknown;
       bit under-repair;
       bit critical;
       bit major;
       bit minor;
       bit warning;
       bit indeterminate;
     }
   }

   leaf alarm-state {
     type alarm-state;
   }

   CBOR diagnostic notation: h'06'

   CBOR encoding: 41 06

   To avoid overlap of 'bit' defined in different 'bits' statements,
   'bits' defined in a Leafs of type 'union' MUST be encoded using a
   CBOR text string data item (major type 3) and MUST contain a space-
   separated sequence of names of 'bit' that are set.  The encoding MUST
   be prefixed with the bits CBOR tag as specified in Section 8.1.

   The following example shows the encoding of an 'alarm-state' leaf
   instance defined using a union type with the 'under-repair' and
   'critical' flags set.

   Definition example:










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   leaf alarm-state-2 {
     type union {
       type alarm-state;
       type bits {
         bit extra-flag;
       }
     }
   }

   CBOR diagnostic notation: 99("under-repair critical")

   CBOR encoding: D8 63 75 756E6465722D72657061697220637269746963616C

   // RFC Ed.: update 99 and D8 63 with the bits CBOR tag allocated.

6.8.  The 'binary' Type

   Leafs of type binary MUST be encoded using a CBOR byte string data
   item (major type 2).

   The following example shows the encoding of an 'aes128-key' leaf
   instance set to 0x1f1ce6a3f42660d888d92a4d8030476e.

   Definition example:

   leaf aes128-key {
     type binary {
       length 16;
     }
   }

   CBOR diagnostic notation: h'1F1CE6A3F42660D888D92A4D8030476E'

   CBOR encoding: 50 1F1CE6A3F42660D888D92A4D8030476E

6.9.  The 'leafref' Type

   Leafs of type leafref MUST be encoded using the rules of the schema
   node referenced by the 'path' YANG statement.

   The following example shows the encoding of an 'interface-state-ref'
   leaf instance set to "eth1".

   Definition example from [RFC7223]:







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   typedef interface-state-ref {
     type leafref {
       path "/interfaces-state/interface/name";
     }
   }

   container interfaces-state {
     list interface {
       key "name";
       leaf name {
         type string;
       }
       leaf-list higher-layer-if {
         type interface-state-ref;
       }
     }
   }

   CBOR diagnostic notation: "eth1"

   CBOR encoding: 64 65746831

6.10.  The 'identityref' Type

   This specification supports two approaches for encoding identityref,
   a YANG Schema Item iDentifier (SID) as defined in Section 3.2 or a
   name as defined in [RFC7951] section 6.8.

6.10.1.  SIDs as identityref

   When schema nodes of type identityref are implemented using SIDs,
   they MUST be encoded using a CBOR unsigned integer data item (major
   type 0).  (Note that no delta mechanism is employed for SIDs as
   identityref.)

   The following example shows the encoding of a 'type' leaf instance
   set to the value 'iana-if-type:ethernetCsmacd' (SID 1880).

   Definition example from [RFC7317]:












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   identity interface-type {
   }

   identity iana-interface-type {
     base interface-type;
   }

   identity ethernetCsmacd {
     base iana-interface-type;
   }

   leaf type {
     type identityref {
       base interface-type;
     }
   }

   CBOR diagnostic notation: 1880

   CBOR encoding: 19 0758

6.10.2.  Name as identityref

   Alternatively, an identityref MAY be encoded using a name as defined
   in Section 3.3.  When names are used, identityref MUST be encoded
   using a CBOR text string data item (major type 3).  If the identity
   is defined in different module than the leaf node containing the
   identityref data node, the namespace qualified form MUST be used.
   Otherwise, both the simple and namespace qualified forms are
   permitted.  Names and namespaces are defined in Section 3.3.

   The following example shows the encoding of the identity 'iana-if-
   type:ethernetCsmacd' using its namespace qualified name.  This
   example is described in Section 6.10.1.

   CBOR diagnostic notation: "iana-if-type:ethernetCsmacd"

   CBOR encoding: 78 1b
   69616E612D69662D747970653A65746865726E657443736D616364

6.11.  The 'empty' Type

   Leafs of type empty MUST be encoded using the CBOR null value (major
   type 7, additional information 22).

   The following example shows the encoding of a 'is-router' leaf
   instance when present.




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   Definition example from [RFC7277]:

   leaf is-router {
     type empty;
   }

   CBOR diagnostic notation: null

   CBOR encoding: F6

6.12.  The 'union' Type

   Leafs of type union MUST be encoded using the rules associated with
   one of the types listed.  When used in a union, the following YANG
   datatypes are prefixed by CBOR tag to avoid confusion between
   different YANG datatypes encoded using the same CBOR major type.

   o  bits

   o  enumeration

   o  identityref

   o  instance-identifier

   See Section 8.1 for the assigned value of these CBOR tags.

   As mentioned in Section 6.6 and in Section 6.7, 'enumeration' and
   'bits' are encoded as CBOR text string data item (major type 3) when
   defined within a 'union' type.

   The following example shows the encoding of an 'ip-address' leaf
   instance when set to "2001:db8:a0b:12f0::1".

   Definition example from [RFC7317]:
















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   typedef ipv4-address {
     type string {
     pattern '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.){3}
              ([0-9][1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(%[\p{N}
              \p{L}]+)?';
     }
   }

   typedef ipv6-address {
     type string {
       pattern '((:|[0-9a-fA-F]{0,4}):)([0-9a-fA-F]{0,4}:){0,5}((([0-9a
                -fA-F]{0,4}:)?(:|[0-9a-fA-F]{0,4}))|(((25[0-5]|2[0-4][0
                -9]|[01]?[0-9]?[0-9])\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0
                -9]?[0-9])))(%[\p{N}\p{L}]+)?';
       pattern '(([^:]+:){6}(([^:]+:[^:]+)|(.*\..*)))|((([^:]+:)*[^:]+)
                ?::(([^:]+:)*[^:]+)?)(%.+)?';
     }
   }

   typedef ip-address {
     type union {
       type ipv4-address;
       type ipv6-address;
     }
   }

   leaf address {
     type inet:ip-address;
   }

   CBOR diagnostic notation: "2001:db8:a0b:12f0::1"

   CBOR encoding: 74 323030313A6462383A6130623A313266303A3A31

6.13.  The 'instance-identifier' Type

   This specification supports two approaches for encoding an instance-
   identifier, one based on YANG Schema Item iDentifier (SID) as defined
   in Section 3.2 and one based on names as defined in Section 3.3.

6.13.1.  SIDs as instance-identifier

   SIDs uniquely identify a schema node.  In the case of a single
   instance schema node, i.e. a schema node defined at the root of a
   YANG module or submodule or schema nodes defined within a container,
   the SID is sufficient to identify this instance.





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   In the case of a schema node member of a YANG list, a SID is combined
   with the list key(s) to identify each instance within the YANG
   list(s).

   Single instance schema nodes MUST be encoded using a CBOR unsigned
   integer data item (major type 0) and set to the targeted schema node
   SID.

   Schema nodes member of a YANG list MUST be encoded using a CBOR array
   data item (major type 4) containing the following entries:

   o  The first entry MUST be encoded as a CBOR unsigned integer data
      item (major type 0) and set to the targeted schema node SID.

   o  The following entries MUST contain the value of each key required
      to identify the instance of the targeted schema node.  These keys
      MUST be ordered as defined in the 'key' YANG statement, starting
      from top level list, and follow by each of the subordinate
      list(s).

   Examples within this section assume the definition of a schema node
   of type 'instance-identifier':

   Definition example from [RFC7950]:

   container system {
     ...
     leaf reporting-entity {
       type instance-identifier;
     }

   leaf contact { type string; }

   leaf hostname { type inet:domain-name; } } ~~~~

   *First example:*

   The following example shows the encoding of the 'reporting-entity'
   value referencing data node instance "/system/contact" (SID 1741).

   Definition example from [RFC7317]:










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   container system {

     leaf contact {
       type string;
     }

     leaf hostname {
       type inet:domain-name;
     }
   }

   CBOR diagnostic notation: 1741

   CBOR encoding: 19 06CD

   *Second example:*

   The following example shows the encoding of the 'reporting-entity'
   value referencing list instance "/system/authentication/user/
   authorized-key/key-data" (SID 1734) for user name "bob" and
   authorized-key "admin".

   Definition example from [RFC7317]:

   list user {
     key name;

     leaf name {
       type string;
     }
     leaf password {
       type ianach:crypt-hash;
     }

     list authorized-key {
       key name;

       leaf name {
         type string;
       }
       leaf algorithm {
         type string;
       }
       leaf key-data {
         type binary;
     }
   }




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   CBOR diagnostic notation: [1734, "bob", "admin"]

   CBOR encoding:

   83               # array(3)
      19 06C6       # unsigned(1734)
      63            # text(3)
         626F62     # "bob"
      65            # text(5)
         61646D696E # "admin"

   *Third example:*

   The following example shows the encoding of the 'reporting-entity'
   value referencing the list instance "/system/authentication/user"
   (SID 1730) corresponding to user name "jack".

   CBOR diagnostic notation: [1730, "jack"]

   CBOR encoding:

   82             # array(2)
      19 06C2     # unsigned(1730)
      64          # text(4)
         6A61636B # "jack"

6.13.2.  Names as instance-identifier

   An "instance-identifier" value is encoded as a string that is
   analogical to the lexical representation in XML encoding; see
   Section 9.13.2 in [RFC7950].  However, the encoding of namespaces in
   instance-identifier values follows the rules stated in Section 3.3,
   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






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   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".

   The resulting xpath MUST be encoded using a CBOR text string data
   item (major type 3).

   *First example:*

   This example is described in Section 6.13.1.

   CBOR diagnostic notation: "/ietf-system:system/contact"

   CBOR encoding:

   78 1c 2F696574662D73797374656D3A73797374656D2F636F6E74616374

   *Second example:*

   This example is described in Section 6.13.1.

   CBOR diagnostic notation:

   "/ietf-system:system/authentication/user[name='bob']/authorized-key
   [name='admin']/key-data"

   CBOR encoding:

   78 59
      2F696574662D73797374656D3A73797374656D2F61757468656E74696361
      74696F6E2F757365725B6E616D653D27626F62275D2F617574686F72697A
      65642D6B65790D0A5B6E616D653D2761646D696E275D2F6B65792D64617461

   *Third example:*

   This example is described in Section 6.13.1.

   CBOR diagnostic notation:

   "/ietf-system:system/authentication/user[name='bob']"

   CBOR encoding:

   78 33
      2F696574662D73797374656D3A73797374656D2F61757468656E74696361
      74696F6E2F757365725B6E616D653D27626F62275D





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7.  Security Considerations

   The security considerations of [RFC7049] and [RFC7950] apply.

   This document defines an alternative encoding for data modeled in the
   YANG data modeling language.  As such, this encoding does not
   contribute any new security issues in addition of those identified
   for the specific protocol or context for which it is used.

   To minimize 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.

8.  IANA Considerations

8.1.  Tags Registry

   This specification requires the assignment of CBOR tags for the
   following YANG datatypes.  These tags are added to the Tags Registry
   as defined in section 7.2 of [RFC7049].

   +-----+---------------------+---------------------------+-----------+
   | Tag | Data Item           | Semantics                 | Reference |
   +-----+---------------------+---------------------------+-----------+
   | xx  | SID                 | YANG Schema Item          | RFC XXXX  |
   |     |                     | iDentifier                |           |
   | xx  | bits                | YANG bits datatype        | RFC XXXX  |
   | xx  | enumeration         | YANG enumeration datatype | RFC XXXX  |
   | xx  | identityref         | YANG identityref datatype | RFC XXXX  |
   | xx  | instance-identifier | YANG instance-identifier  | RFC XXXX  |
   |     |                     | datatype                  |           |
   +-----+---------------------+---------------------------+-----------+

   // RFC Ed.: update Tag values using allocated tags and remove this
   note // RFC Ed.: replace XXXX with RFC number and remove this note

9.  Acknowledgments

   This document has been largely inspired by the extensive works done
   by Andy Bierman and Peter van der Stok on [I-D.ietf-core-comi].
   [RFC7951] has also been a critical input to this work.  The authors
   would like to thank the authors and contributors to these two drafts.

   The authors would also like to acknowledge the review, feedback, and
   comments from Ladislav Lhotka and Juergen Schoenwaelder.






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10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

10.2.  Informative References

   [I-D.ietf-core-comi]
              Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
              Management Interface", draft-ietf-core-comi-04 (work in
              progress), November 2018.

   [I-D.ietf-core-sid]
              Veillette, M., Pelov, A., and I. Petrov, "YANG Schema Item
              iDentifier (SID)", draft-ietf-core-sid-06 (work in
              progress), March 2019.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/info/rfc7159>.

   [RFC7223]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
              <https://www.rfc-editor.org/info/rfc7223>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <https://www.rfc-editor.org/info/rfc7228>.





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   [RFC7277]  Bjorklund, M., "A YANG Data Model for IP Management",
              RFC 7277, DOI 10.17487/RFC7277, June 2014,
              <https://www.rfc-editor.org/info/rfc7277>.

   [RFC7317]  Bierman, A. and M. Bjorklund, "A YANG Data Model for
              System Management", RFC 7317, DOI 10.17487/RFC7317, August
              2014, <https://www.rfc-editor.org/info/rfc7317>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8348]  Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
              YANG Data Model for Hardware Management", RFC 8348,
              DOI 10.17487/RFC8348, March 2018,
              <https://www.rfc-editor.org/info/rfc8348>.

Authors' Addresses

   Michel Veillette (editor)
   Trilliant Networks Inc.
   610 Rue du Luxembourg
   Granby, Quebec  J2J 2V2
   Canada

   Email: michel.veillette@trilliantinc.com


   Ivaylo Petrov (editor)
   Acklio
   1137A avenue des Champs Blancs
   Cesson-Sevigne, Bretagne  35510
   France

   Email: ivaylo@ackl.io


   Alexander Pelov
   Acklio
   1137A avenue des Champs Blancs
   Cesson-Sevigne, Bretagne  35510
   France

   Email: a@ackl.io



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