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Versions: 00 draft-ietf-core-yang-cbor

Internet Engineering Task Force                        M. Veillette, Ed.
Internet-Draft                                   Trilliant Networks Inc.
Intended status: Informational                             A. Pelov, Ed.
Expires: September 12, 2016                                       Acklio
                                                             A. Somaraju
                                                   Tridonic GmbH & Co KG
                                                               R. Turner
                                                              Landis+Gyr
                                                             A. Minaburo
                                                                  Acklio
                                                          March 11, 2016


                CBOR Encoding of Data Modeled with YANG
               draft-veillette-core-yang-cbor-mapping-00

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 http://datatracker.ietf.org/drafts/current/.

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

   This Internet-Draft will expire on September 12, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   3
     2.1.  CBOR diagnostic notation  . . . . . . . . . . . . . . . .   4
   3.  Properties of the CBOR Encoding . . . . . . . . . . . . . . .   5
   4.  Encoding of YANG Schema Node Instances  . . . . . . . . . . .   6
     4.1.  The "leaf" Schema Node  . . . . . . . . . . . . . . . . .   6
     4.2.  The "container" Schema Node . . . . . . . . . . . . . . .   6
     4.3.  The "leaf-list" Schema Node . . . . . . . . . . . . . . .   9
     4.4.  The "list" Schema Node  . . . . . . . . . . . . . . . . .  10
     4.5.  The "anydata" Schema Node . . . . . . . . . . . . . . . .  16
     4.6.  The "anyxml" Schema Node  . . . . . . . . . . . . . . . .  17
   5.  Representing YANG Data Types in CBOR  . . . . . . . . . . . .  17
     5.1.  The unsigned integer Types  . . . . . . . . . . . . . . .  17
     5.2.  The integer Types . . . . . . . . . . . . . . . . . . . .  17
     5.3.  The "decimal64" Type  . . . . . . . . . . . . . . . . . .  18
     5.4.  The "string" Type . . . . . . . . . . . . . . . . . . . .  18
     5.5.  The "boolean" Type  . . . . . . . . . . . . . . . . . . .  19
     5.6.  The "enumeration" Type  . . . . . . . . . . . . . . . . .  19
     5.7.  The "bits" Type . . . . . . . . . . . . . . . . . . . . .  19
     5.8.  The "binary" Type . . . . . . . . . . . . . . . . . . . .  20
     5.9.  The "leafref" Type  . . . . . . . . . . . . . . . . . . .  20
     5.10. The "identityref" Type  . . . . . . . . . . . . . . . . .  21
     5.11. The "empty" Type  . . . . . . . . . . . . . . . . . . . .  22
     5.12. The "union" Type  . . . . . . . . . . . . . . . . . . . .  23
     5.13. The "instance-identifier" Type  . . . . . . . . . . . . .  23
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  28
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  29
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  29
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   The specification of the YANG 1.1 data modelling language
   [I-D.ietf-netmod-rfc6020bis] defines only 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.



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   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 [I-D.ietf-netmod-yang-json].

   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 [I-D.ietf-netmod-rfc6020bis]:

   o  action

   o  anydata

   o  anyxml

   o  data node

   o  data tree

   o  module

   o  notification

   o  RPC

   o  schema node

   o  schema tree

   o  submodule

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

   o  member name

   o  name of an identity




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   The following term is defined in [I-D.vanderstok-core-comi]:

   o  YANG hash

   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 SID assigned to the current schema
      node and the SID assigned to the parent.

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

   o  structured identifier or SID: Unsigned integer used to identify
      different YANG items.

2.1.  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.



























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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 |      |                          |           |          |
   +----------+------+--------------------------+-----------+----------+

   Within this document, comments are allowed in CBOR diagnostic
   notation.  Any characters after a Pound sign ('#') outside of a
   string, up to the end of the line, are treated as a comment.

3.  Properties of the CBOR Encoding

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

   Basic schema nodes such as leaf, leaf-list, list, anydata and anyxml
   can be encoded standalone.  In this case, only the value of this
   schema node is encoded in CBOR.  Identification of this value need to
   be provided by some external means when needed.

   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 three type of keys; SID as
   defined in [I-D.somaraju-core-sid], member names as defined in
   [I-D.ietf-netmod-yang-json] and YANG hash as defined by



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   [I-D.vanderstok-core-comi].  Each of these key type is encoded using
   a specific CBOR type which allows their interpretation during the
   deserialization process.  The end user of this mapping specification
   can mandate the use of a specific key type or a specific subset of
   key types.

   In order to minimize the size of the encoded data, the proposed
   mapping does not make use of any meta-information beyond those
   natively supported by CBOR.  For instance, CBOR tags are not used for
   any of the proposed mapping.  It is expected that entities generating
   and decoding CBOR contents have enough knowledge about the
   information processed in order to perform the expected task without
   the need of such extra meta-information.  The CoAP Content-Format
   Option, or an HTTP Content-Type header field, conveys that the data
   is YANG-encoded CBOR in the first place.

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 [I-D.ietf-netmod-rfc6020bis] and CBOR [RFC7049].

4.1.  The "leaf" Schema Node

   Leafs MUST be encoded based on the encoding rules specified in
   Section 5.

4.2.  The "container" Schema Node

   Collections such as containers, list instances, notifications, 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.  This specification supports three type of keys; SID as
   defined in [I-D.somaraju-core-sid], member names as defined in
   [I-D.ietf-netmod-yang-json] and YANG hash as defined by
   [I-D.vanderstok-core-comi].

   *SIDs as keys*

   Keys implemented using SIDs MUST be encoded using a CBOR unsigned
   integer (major type 0) and set to the delta value of the associated
   SID.  Delta values are computed as follows:

   o  The delta value is equal to the SID of the current schema node
      minus the SID of the parent schema node.  When no parent exists in
      the context of use of this container, the delta is set to the SID



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      of the current schema node (a parent with SID equal to zero is
      assumed).

   o  Delta values may result in a negative number, clients and servers
      MUST support negative deltas.

   *Member names as keys*

   Keys implemented using member names MUST be encoded using a CBOR text
   string data item (major type 3).  A namespace-qualified member name
   MUST be used for all members of a top-level collection, and then also
   whenever the namespaces of the schema node and its parent are
   different.  In all other cases, the simple form of the member name
   MUST be used.  Member names and namespaces are defined in
   [I-D.ietf-netmod-yang-json] section 4.

   *YANG hashes as keys*

   Keys implemented using YANG hashes MUST be encoded using a CBOR byte
   string data item (major type 2).

   Values MUST be encoded using the appropriate rules defined in
   Section 4 and Section 5.

   Definition example [RFC7317]:

   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 {
     leaf hostname {
       type inet:domain-name;

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

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




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   *SIDs example*

   This example is encoded using the SIDs defined in [I-D.somaraju-core-
   sid] Appendix C.

   CBOR diagnostic notation:

   {
     1708 : {                              # clock
       2 : "2015-10-02T14:47:24Z-05:00",   # current-datetime, SID 1710
       1 : "2015-09-15T09:12:58Z-05:00"    # boot-datetime, SID 1709
     }
   }

   CBOR encoding:

   a1                                      # map(1)
      19 06ac                              # unsigned(1708)
      a2                                   # map(2)
         02                                # unsigned(2)
         78 1a                             # text(26)
         323031352d31302d30325431343a34373a32345a2d30353a3030
         01                                # unsigned(1)
         78 1a                             # text(26)
         323031352d30392d31355430393a31323a35385a2d30353a3030

   *Member names example*

   CBOR diagnostic notation:

   {
     "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)
      71                                       # text(17)
         696574662d73797374656d3a636c6f636b    # "ietf-system:clock"
      a2                                       # map(2)
         70                                    # text(16)
            63757272656e742d6461746574696d65   # "current-datetime"
         78 1a                                 # text(26)
            323031352d31302d30325431343a34373a32345a2d30353a3030
         6d                                    # text(13)
            626f6f742d6461746574696d65         # "boot-datetime"
         78 1a                                 # text(26)
            323031352d30392d31355430393a31323a35385a2d30353a3030

   *YANG Hashes example*

   CBOR diagnostic notation:

   {
     h'334c67d9' : {                                # clock
       h'047c468b' : "2015-10-02T14:47:24Z-05:00",  # current-datetime
       h'2fe1a167' : "2015-09-15T09:12:58Z-05:00"   # boot-datetime
     }
   }

   CBOR encoding:

   a1                                      # map(1)
      44                                   # bytes(4)
         334c67d9
      a2                                   # map(2)
         44                                # bytes(4)
            047c468b
         78 1a                             # text(26)
            323031352d31302d30325431343a34373a32345a2d30353a3030
         44                                # bytes(4)
            2fe1a167
         78 1a                             # text(26)
            323031352d30392d31355430393a31323a35385a2d30353a3030

4.3.  The "leaf-list" Schema Node

   A leaf-list MUST be encoded using a CBOR array data item (major type
   4).  Each entry of this array MUST be encoded using the rules defined
   by the YANG type specified.

   Definition example [RFC7317]:





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   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

4.4.  The "list" Schema Node

   A list MUST be encoded using a CBOR array data item (major type 4).
   Each entry of this array is encoded using a CBOR map data item (major
   type 5) based on the same rules as a YANG container, see Section 4.2.

   Definition example [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;
     }
   }

   *SIDs example*

   SIDs used in this example are defined in [I-D.somaraju-core-sid]
   Appendix C.  It is important to note that the protocol or method
   using this mapping may carry a parent SID or may have the knowledge
   of this parent SID based on its context.  In these cases, delta
   encoding can be performed based on this parent SID which minimizes
   the size of the encoded data.

   CBOR diagnostic notation:




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   [
     {
       1746 : "NRC TIC server",          # name
       1748 : {                          # udp
         1 : "tic.nrc.ca",               # address, SID 1749
         2 : 123                         # port, SID 1750
       },
       1744 : 0,                         # association-type
       1745 : false,                     # iburst
       1747 : true                       # prefer
     },
     {
       1746 : "NRC TAC server",          # name
       1748 : {                          # udp
         1 : "tac.nrc.ca"                # address, SID 1749
       }
     }
   ]

   CBOR encoding:

   82                                    # array(2)
      a5                                 # map(5)
         19 06d2                         # unsigned(1746)
         6e                              # text(14)
            4e52432054494320736572766572 # "NRC TIC server"
         19 06d4                         # unsigned(1748)
         a2                              # map(2)
            01                           # unsigned(1)
            6a                           # text(10)
               7469632e6e72632e6361      # "tic.nrc.ca"
            02                           # unsigned(2)
            18 7b                        # unsigned(123)
         19 06d0                         # unsigned(1744)
         00                              # unsigned(0)
         19 06d1                         # unsigned(1745)
         f4                              # primitive(20)
         19 06d3                         # unsigned(1747)
         f5                              # primitive(21)
      a2                                 # map(2)
         19 06d2                         # unsigned(1746)
         6e                              # text(14)
            4e52432054414320736572766572 # "NRC TAC server"
         19 06d4                         # unsigned(1748)
         a1                              # map(1)
            01                           # unsigned(1)
            6a                           # text(10)
               7461632e6e72632e6361      # "tac.nrc.ca"



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   *Member names example*

   CBOR diagnostic notation:

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

   CBOR encoding:



























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   82                                            # array(2)
      a5                                         # map(5)
         70                                      # text(16)
            696574662d73797374656d3a6e616d65     # "ietf-system:name"
         6e                                      # text(14)
            4e52432054494320736572766572         # "NRC TIC server"
         6f                                      # text(15)
            696574662d73797374656d3a756470       # "ietf-system: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)
         78 1c                                   # text(28)
            696574662d73797374656d3a6173736f63696174696f6e2d74797065
         00                                      # unsigned(0)
         72                                      # text(18)
            696574662d73797374656d3a696275727374 # "ietf-system:iburst"
         f4                                      # primitive(20)
         72                                      # text(18)
            696574662d73797374656d3a707265666572 # "ietf-system:prefer"
         f5                                      # primitive(21)
      a2                                         # map(2)
         70                                      # text(16)
            696574662d73797374656d3a6e616d65     # "ietf-system:name"
         6e                                      # text(14)
            4e52432054414320736572766572         # "NRC TAC server"
         6f                                      # text(15)
            696574662d73797374656d3a756470       # "ietf-system:udp"
         a1                                      # map(1)
            67                                   # text(7)
               61646472657373                    # "address"
            6a                                   # text(10)
               7461632e6e72632e6361              # "tac.nrc.ca"

   *YANG hashes example*

   CBOR diagnostic notation:










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   [
     {
       h'06c32032' : "NRC TIC server",           # name
       h'11889c84' : {                           # udp
         h'3158c529' : "tic.nrc.ca",             # address
         h'34492d05' : 123                       # port
       },
       h'2c2c2ccf' : 0,                          # association-type
       h'1058dc5d' : false,                      # iburst
       h'390e346a' : true                        # prefer
     },
     {
       h'06c32032' : "NRC TAC server",           # name
       h'11889c84' : {                           # udp
         h'3158c529' : "tac.nrc.ca"              # address
       }
     }
   ]

   CBOR encoding:































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   82                                    # array(2)
      a5                                 # map(5)
         44                              # bytes(4)
            06c32032"
         6e                              # text(14)
            4e52432054494320736572766572 # "NRC TIC server"
         44                              # bytes(4)
            11889c84 "
         a2                              # map(2)
            44                           # bytes(4)
               3158c529
            6a                           # text(10)
               7469632e6e72632e6361      # "tic.nrc.ca"
            44                           # bytes(4)
               34492d05
            18 7b                        # unsigned(123)
         44                              # bytes(4)
            2c2c2ccf
         00                              # unsigned(0)
         44                              # bytes(4)
            1058dc5d
         f4                              # primitive(20)
         44                              # bytes(4)
            390e346a
         f5                              # primitive(21)
      a2                                 # map(2)
         44                              # bytes(4)
            06c32032
         6e                              # text(14)
            4e52432054414320736572766572 # "NRC TAC server"
         44                              # bytes(4)
            11889c84
         a1                              # map(1)
            44                           # bytes(4)
               3158c529
            6a                           # text(10)
               7461632e6e72632e6361      # "tac.nrc.ca"

4.5.  The "anydata" Schema Node

   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  Keys MUST be set to valid SIDs, member names or YANG hashes.  This
      rule applies to the key of the anydata node and the key of any
      inner schema node.

   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  Values MUST follow the encoding rules of one of the datatypes
      listed in Section 5.

4.6.  The "anyxml" Schema Node

   An anyxml instance is encoded as a CBOR key/value pair.  The key of
   the anyxml schema node MUST be a valid SID, member name or YANG hash
   but the value is unrestricted, i.e., the value can be any CBOR
   encoded content.

5.  Representing YANG Data Types in CBOR

5.1.  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).

   Definition example [RFC7277]:

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

   CBOR diagnostic notation: 1280

   CBOR encoding: 19 0500

5.2.  The integer Types

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

   Definition example [RFC7317]:








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

   CBOR diagnostic notation: -300

   CBOR encoding: 39 012b

5.3.  The "decimal64" Type

   Leafs of type decimal64 MUST be encoded using either CBOR unsigned
   integer (major type 0) or CBOR signed integer (major type 1),
   depending on the actual value.  The position of the decimal point is
   defined by the fraction-digits YANG statement and is not available in
   the CBOR encoding.

   Definition example [RFC7317]:

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

   CBOR diagnostic notation: 257 (Represents decimal value 2.57)

   CBOR encoding: 19 0101

5.4.  The "string" Type

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

   Definition example [RFC7223]:

   leaf name {
     type string;
   }

   CBOR diagnostic notation: "eth0"

   CBOR encoding: 64 65746830






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5.5.  The "boolean" Type

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

   Definition example [RFC7317]:

   leaf enabled {
     type boolean;
   }

   CBOR diagnostic notation: true

   CBOR encoding: f5

5.6.  The "enumeration" Type

   Leafs of type enumeration MUST be encoded using a CBOR unsigned
   integer data item (major type 0).

   Definition example [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 (Represents enumeration value "testing")

   CBOR encoding: 03

5.7.  The "bits" Type

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

   Definition example [I-D.ietf-netmod-rfc6020bis]:



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   leaf mybits {
     type bits {
       bit disable-nagle {
         position 0;
       }
       bit auto-sense-speed {
         position 1;
       }
       bit 10-Mb-only {
         position 2;
       }
     }
   }

   CBOR diagnostic notation: h'05' (Represents bits disable-nagle and
   10-Mb-only set)

   CBOR encoding: 41 05

5.8.  The "binary" Type

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

   Definition example:

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

   CBOR diagnostic notation: h'1f1ce6a3f42660d888d92a4d8030476e'

   CBOR encoding: 50 1f1ce6a3f42660d888d92a4d8030476e

5.9.  The "leafref" Type

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

   Definition example [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

5.10.  The "identityref" Type

   This specification supports two approaches for encoding identityref,
   a SID as defined in [I-D.somaraju-core-sid] or a name as defined in
   [I-D.ietf-netmod-yang-json] section 6.8.

   *SIDs as identityref*

   SIDs are globally unique and may be used as identityref.  This
   approach is both compact and simple to implement.  When SIDs are
   used, identityref MUST be encoded using a CBOR unsigned integer data
   item (major type 0) and set to a SID allocated from a registered SID
   range.

   *Name as identityref*

   Alternatively, an identityref may be encoded using a name as defined
   in [I-D.ietf-netmod-yang-json] section 6.8.  When names are used,
   identityref MUST be encoded using a CBOR text string data item (major
   type 3).  If the identity is defined in another module than the leaf
   node containing the identityref value, the namespace-qualified form
   MUST be used.  Otherwise, both the simple and namespace-qualified
   forms are permitted.

   Definition example [RFC7223]:




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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;
     }
   }

   *SIDs as identityref*

   Assuming that the identity "iana-if-type:ethernetCsmacd" has been
   assigned to the SID value 1179.

   CBOR diagnostic notation: 1179

   CBOR encoding: 19 049b

   *Name as identityref*

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

   CBOR encoding: 78 1b
   69616e612d69662d747970653a65746865726e657443736d616364

5.11.  The "empty" Type

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

   Definition example [RFC7277]:

   leaf is-router {
     type empty;
   }

   CBOR diagnostic notation: null

   CBOR encoding: f6




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5.12.  The "union" Type

   Leafs of type union MUST be encoded using the rules associated with
   one of the types listed.

   Definition example [RFC7317]:

   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

5.13.  The "instance-identifier" Type

   This specification supports three approaches for encoding an
   instance-identifier, one based on SIDs as defined in [I-D.somaraju-
   core-sid], one based on names as defined in
   [I-D.ietf-netmod-yang-json] section 6.13 and one based on YANG hashes
   as defined in [I-D.vanderstok-core-comi].



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   *SIDs as instance-identifier*

   SIDs uniquely identify a data node.  For a single instance data node,
   the SID is sufficient to identify this instance.  For a multi-
   instance data node, a SID is combined with the list key(s) to
   identify each instance of this data node within the YANG list(s).

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

   Multi-instances data nodes 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 data node SID.

   o  The following entries MUST contain the value of each key required
      to identify the instance of the targeted data 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).

   When SIDs identify a YANG list, the presence of the key(s) for this
   list is optional.  When the key(s) are present, the targeted instance
   within this list is selected.  When the key(s) are absent, the entire
   YANG list is selected.

   *Names as instance-identifier*

   The use of names as instance-identifier is defined in
   [I-D.ietf-netmod-yang-json] section 6.11.  The resulting xpath MUST
   be encoded using a CBOR text string data item (major type 3).

   *YANG hashes as instance-identifier*

   When YANG hashes are used, xpath can be compressed based on the
   method defined by [I-D.vanderstok-core-comi] sections 4.1.4.1 and
   4.1.4.2.

   Definition example [RFC7317]:










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   container system {

     leaf contact {
       type string;
     }

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

   *First example based on SID*

   In this example, a field of type instance-identifier identifies the
   data node "/system/contact" (SID 1728).

   1728

   CBOR encoding:

   19 06c0

   *First example based on name*

   Same example as above based on names.

   "/ietf-system:system/contact"

   CBOR encoding:

   78 1c 2f20696574662d73797374656d3a73797374656d2f636f6e74616374

   *First example based on YANG hash*

   Same example assuming data node "/system/contact" is associated to
   YANG hash 0x09b06d17 or "JsG0X" in base64.

   CBOR diagnostic notation:

   "/JsG0X"

   CBOR encoding:

   66 2f4a73473058

   Definition example [RFC7317]:





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   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;
     }
   }

   *Second example based on SID*

   In this example, a field of type instance-identifier identify the
   data node "/system/authentication/user/authorized-key/key-data" (SID
   1721) for the user name "bob" and the authorized-key name "admin".

   CBOR diagnostic notation:

   [1721, "bob", "admin"]

   CBOR encoding:

   83                      # array(3)
      19 06b9              # unsigned(1721)
      63                   # text(3)
         626f62            # "bob"
      65                   # text(5)
         61646d696e        # "admin"

   *Second example based on name*

   Same example as above based on names.

   CBOR diagnostic notation:



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

   CBOR encoding:

   78 59
      2f696574662d73797374656d3a73797374656d2f61757468656e74696361
      74696f6e2f757365725b6e616d653d27626f62275d2f617574686f72697a
      65642d6b65795b6e616d653d2761646d696e275d2f6b65792d64617461

   *Second example based on YANG hash*

   Same example assuming data node "/ietf-
   system:system/authentication/user/authorized-key/key-data" is
   associated to YANG hash 0x0d6e7afb or "Nbnr7" in base64.

   CBOR diagnostic notation:

   "/Nbnr7?keys=\"bob\",\"admin\""

   CBOR encoding:

   78 19 2f4e626e72373f6b6579733d22626f62222c2261646d696e22

   *Third example based on SID*

   This third example identify an instance within the list
   "/system/authentication/user" (SID 1717) corresponding to the user
   name "jack".

   CBOR diagnostic notation:

   [1717, "jack"]

   CBOR encoding:

   82                      # array(2)
      19 06b5              # unsigned(1717)
      64                   # text(4)
         6a61636b          # "jack"

   *Third example based on name*

   Same example as above based on names.

   CBOR diagnostic notation:

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



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   CBOR encoding:

   78 33
      2f696574662d73797374656d3a73797374656d2f61757468656e74696361
      74696f6e2f757365725b6e616d653d27626f62275d

   *Third example based on YANG hash*

   Same example assuming data node "/ietf-system:system/authentication/
   user" is associated to YANG hash 0x2677c6c1 or "md8bB" in base64.

   CBOR diagnostic notation:

   "/md8bB?keys=\"bob\""

   CBOR encoding:

   71 2f6d643862423f6b6579733d22626f6222

6.  Security Considerations

   The security considerations of [RFC7049] and
   [I-D.ietf-netmod-rfc6020bis] 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.

7.  Acknowledgments

   This document has been largely inspired by the extensive works done
   by Andy Bierman and Peter van der Stok on [I-D.vanderstok-core-comi].
   [I-D.ietf-netmod-yang-json] 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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8.  References

8.1.  Normative References

   [I-D.ietf-netmod-rfc6020bis]
              Bjorklund, M., "The YANG 1.1 Data Modeling Language",
              draft-ietf-netmod-rfc6020bis-11 (work in progress),
              February 2016.

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

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

8.2.  Informative References

   [I-D.ietf-netmod-yang-json]
              Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              draft-ietf-netmod-yang-json-09 (work in progress), March
              2016.

   [I-D.vanderstok-core-comi]
              Stok, P. and A. Bierman, "CoAP Management Interface",
              draft-vanderstok-core-comi-09 (work in progress), March
              2016.

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

   [RFC7223]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
              <http://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,
              <http://www.rfc-editor.org/info/rfc7228>.

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





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

Authors' Addresses

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

   Phone: +14503750556
   Email: michel.veillette@trilliantinc.com


   Alexander Pelov (editor)
   Acklio
   2bis rue de la Chataigneraie
   Cesson-Sevigne, Bretagne  35510
   France

   Email: a@ackl.io


   Abhinav Somaraju
   Tridonic GmbH & Co KG
   Farbergasse 15
   Dornbirn, Vorarlberg  6850
   Austria

   Phone: +43664808926169
   Email: abhinav.somaraju@tridonic.com


   Randy Turner
   Landis+Gyr
   30000 Mill Creek Ave
   Suite 100
   Alpharetta, GA  30022
   US

   Phone: ++16782581292
   Email: randy.turner@landisgyr.com
   URI:   http://www.landisgyr.com/






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   Ana Minaburo
   Acklio
   2bis rue de la chataigneraie
   Cesson-Sevigne, Bretagne  35510
   France

   Email: ana@ackl.io












































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