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Internet Engineering Task Force M. Veillette, Ed.
Internet-Draft Trilliant Networks Inc.
Intended status: Standards Track A. Pelov, Ed.
Expires: May 4, 2017 Acklio
A. Somaraju
Tridonic GmbH & Co KG
R. Turner
Landis+Gyr
A. Minaburo
Acklio
October 31, 2016
CBOR Encoding of Data Modeled with YANG
draft-ietf-core-yang-cbor-03
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 May 4, 2017.
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3
2.1. CBOR diagnostic notation . . . . . . . . . . . . . . . . 4
3. Properties of the CBOR Encoding . . . . . . . . . . . . . . . 5
4. Encoding of YANG Data Node Instances . . . . . . . . . . . . 6
4.1. The 'leaf' Data Node . . . . . . . . . . . . . . . . . . 6
4.2. The 'container' Data Node . . . . . . . . . . . . . . . . 6
4.2.1. SIDs as keys . . . . . . . . . . . . . . . . . . . . 7
4.2.2. Member names as keys . . . . . . . . . . . . . . . . 8
4.3. The 'leaf-list' Data Node . . . . . . . . . . . . . . . . 9
4.4. The 'list' Data Node . . . . . . . . . . . . . . . . . . 9
4.4.1. SIDs as keys . . . . . . . . . . . . . . . . . . . . 10
4.4.2. Member names as keys . . . . . . . . . . . . . . . . 13
4.5. The 'anydata' Data Node . . . . . . . . . . . . . . . . . 14
4.6. The 'anyxml' Data Node . . . . . . . . . . . . . . . . . 15
5. Representing YANG Data Types in CBOR . . . . . . . . . . . . 15
5.1. The unsigned integer Types . . . . . . . . . . . . . . . 15
5.2. The integer Types . . . . . . . . . . . . . . . . . . . . 15
5.3. The 'decimal64' Type . . . . . . . . . . . . . . . . . . 16
5.4. The 'string' Type . . . . . . . . . . . . . . . . . . . . 16
5.5. The 'boolean' Type . . . . . . . . . . . . . . . . . . . 17
5.6. The 'enumeration' Type . . . . . . . . . . . . . . . . . 17
5.7. The 'bits' Type . . . . . . . . . . . . . . . . . . . . . 18
5.8. The 'binary' Type . . . . . . . . . . . . . . . . . . . . 18
5.9. The 'leafref' Type . . . . . . . . . . . . . . . . . . . 19
5.10. The 'identityref' Type . . . . . . . . . . . . . . . . . 19
5.10.1. SIDs as identityref . . . . . . . . . . . . . . . . 20
5.10.2. Name as identityref . . . . . . . . . . . . . . . . 20
5.11. The 'empty' Type . . . . . . . . . . . . . . . . . . . . 21
5.12. The 'union' Type . . . . . . . . . . . . . . . . . . . . 21
5.13. The 'instance-identifier' Type . . . . . . . . . . . . . 22
5.13.1. SIDs as instance-identifier . . . . . . . . . . . . 22
5.13.2. Names as instance-identifier . . . . . . . . . . . . 25
6. Security Considerations . . . . . . . . . . . . . . . . . . . 26
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
7.1. Tags Registry . . . . . . . . . . . . . . . . . . . . . . 26
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
9.1. Normative References . . . . . . . . . . . . . . . . . . 27
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9.2. Informative References . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
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 module
o notification
o RPC
o schema node
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o schema tree
o submodule
The following terms are defined in [RFC7951]:
o member name
o name of an identity
o namespace-qualified
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.
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 Comments can be added to the end of each line. Any characters
after a Pound sign ('#') outside of a string, up to the end of the
line, are treated as a comment.
o Deltas are represented 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. Properties of the CBOR Encoding
This document defines CBOR encoding rules for YANG schema trees and
their subtrees.
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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 needs
to be provided by some external means when required.
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 keys; SID as
defined in [I-D.ietf-core-sid] and member names as defined in
[RFC7951]. 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 (e.g. RESFCONF,
CoMI) can mandate the use of a specific key type.
In order to minimize the size of the encoded data, the proposed
mapping avoid any unnecessary meta-information beyond those natively
supported by CBOR. For instance, CBOR tags are used solely in the
case of the union datatype to distinguish explicitly the use of
different YANG datatypes encoded using the same CBOR major type.
It is expected that application 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.
4. Encoding of YANG Data 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' Data Node
Leafs MUST be encoded based on the encoding rules specified in
Section 5.
4.2. The 'container' Data 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. Each key within the CBOR map is set to a data node
identifier, each value is set to the value of this data node
instance.
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This specification supports two type of keys; SID as defined in
[I-D.ietf-core-sid] encoded using CBOR unsigned or signed integers
and member names as defined in [RFC7951] encoded using CBOR text
strings. The use of CBOR byte strings for keys is reserved for
future extensions.
4.2.1. SIDs as keys
Keys implemented using SIDs MUST be encoded using a CBOR unsigned
integer (major type 0) or CBOR signed integer (major type 1),
depending on the actual value. Keys are set to the delta 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
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.
The following example shows the encoding of the 'system' container
using the SIDs defined in [I-D.ietf-core-sid] Appendix C.
Definition example from [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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CBOR diagnostic notation:
{
1717 : { # clock (SID 1717)
+2 : "2015-10-02T14:47:24Z-05:00", # current-datetime (SID 1719)
+1 : "2015-09-15T09:12:58Z-05:00" # boot-datetime (SID 1718)
}
}
CBOR encoding:
a1 # map(1)
19 06b5 # unsigned(1717)
a2 # map(2)
02 # unsigned(2)
78 1a # text(26)
323031352d31302d30325431343a34373a32345a2d30353a3030
01 # unsigned(1)
78 1a # text(26)
323031352d30392d31355430393a31323a35385a2d30353a3030
4.2.2. 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. Names and namespaces are defined in [RFC7951] section
4.
The following example shows the encoding of the 'system' container
using names. This example is described in Section 4.2.1.
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
4.3. The 'leaf-list' Data 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.
The following example shows the encoding the 'search' leaf-list
containing the 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
4.4. The 'list' Data Node
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 same rules as a YANG container
as defined in Section 4.2.
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4.4.1. SIDs as keys
The follwoing example show the encoding a the 'server' list using the
SIDs defined in [I-D.ietf-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.
The following example shows the encoding of the 'server' list
containing two enties. SIDs used in this example are defined in
[I-D.ietf-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.
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;
}
}
CBOR diagnostic notation:
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[
{
1755 : "NRC TIC server", # name (SID 1755)
1757 : { # udp (SID 1757)
+1 : "tic.nrc.ca", # address (SID 1758)
+2 : 123 # port (SID 1759)
},
1753 : 0, # association-type (SID 1753)
1754 : false, # iburst (SID 1754)
1756 : true # prefer (SID 1756)
},
{
1755 : "NRC TAC server", # name (SID 1755)
1757 : { # udp (SID 1757)
+1 : "tac.nrc.ca" # address (SID 1758)
}
}
]
CBOR encoding:
82 # array(2)
a5 # map(5)
19 06db # unsigned(1755)
6e # text(14)
4e52432054494320736572766572 # "NRC TIC server"
19 06dd # unsigned(1757)
a2 # map(2)
01 # unsigned(1)
6a # text(10)
7469632e6e72632e6361 # "tic.nrc.ca"
02 # unsigned(2)
18 7b # unsigned(123)
19 06d9 # unsigned(1753)
00 # unsigned(0)
19 06da # unsigned(1754)
f4 # primitive(20)
19 06dc # unsigned(1756)
f5 # primitive(21)
a2 # map(2)
19 06db # unsigned(1755)
6e # text(14)
4e52432054414320736572766572 # "NRC TAC server"
19 06dd # unsigned(1757)
a1 # map(1)
01 # unsigned(1)
6a # text(10)
7461632e6e72632e6361 # "tac.nrc.ca"
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4.4.2. Member names as keys
The following example shows the encoding of the 'server' list using
names. This example is described in Section 4.4.1.
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"
4.5. The 'anydata' Data 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:
o Keys of any inner data nodes MUST be set to valid deltas or member
names.
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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' Data Node
An anyxml schema node is used to serialize an arbitrary CBOR content,
i.e., its value can be any CBOR binary object.
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).
The following example shows the encoding of leaf 'mtu' set to 1280
bytes.
Definition example from [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.
The following example shows the encoding of leaf 'timezone-utc-
offset' set to -300 minutes.
Definition example from [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 a decimal fraction as
defined in [RFC7049] section 2.4.3.
The following example shows the encoding of leaf 'my-decimal' 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
5.4. 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 leaf 'name' set to
"eth0".
Definition example from [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).
The following example shows the encoding of leaf 'enabled' set to
'true'.
Definition example from [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 (major type 0) or CBOR signed 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 leaf 'oper-status' set to
'testing'.
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
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5.7. 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.
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 leaf 'mybits' with the
'disable-nagle' and '10-Mb-only' flags set.
Definition example from [RFC7950]:
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'
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).
The following example shows the encoding of leaf 'aes128-key' set to
0x1f1ce6a3f42660d888d92a4d8030476e.
Definition example:
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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.
The following example shows the encoding of leaf 'interface-state-
ref' set to the value "eth1".
Definition example from [RFC7223]:
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.ietf-core-sid] or a name as defined in
[RFC7951] section 6.8.
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5.10.1. 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.
The following example shows the encoding of leaf 'type' set to the
value 'iana-if-type:ethernetCsmacd' (SID 1180).
Definition example from [RFC7317]:
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: 1180
CBOR encoding: 19 049c
5.10.2. Name as identityref
Alternatively, an identityref may be encoded using a name as defined
in [RFC7951] 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. Names and namespaces are defined in [RFC7951] section 4.
The following example shows the encoding of the identity 'iana-if-
type:ethernetCsmacd' using its name. This example is described in
Section 5.10.1.
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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).
The following example shows the encoding of leaf 'is-router' when
present.
Definition example from [RFC7277]:
leaf is-router {
type empty;
}
CBOR diagnostic notation: null
CBOR encoding: f6
5.12. 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 7.1 for more information about these CBOR tags.
The following example shows the encoding of leaf 'ip-address' 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
5.13. The 'instance-identifier' Type
This specification supports two approaches for encoding an instance-
identifier, one based on SIDs as defined in [I-D.ietf-core-sid] and
one based on names as defined in [RFC7951] section 6.11.
5.13.1. SIDs as instance-identifier
SIDs uniquely identify a data node. In the case of a single instance
data node, a data node defined at the root of a YANG module or
submodule or data nodes defined within a container, the SID is
sufficient to identify this instance.
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In the case of a data 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 data nodes MUST be encoded using a CBOR unsigned
integer data item (major type 0) and set to the targeted data node
SID.
Data 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 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).
*First example:*
The following example shows the encoding of a leaf of type instance-
identifier which identify the data node "/system/contact" (SID 1737).
Definition example from [RFC7317]:
container system {
leaf contact {
type string;
}
leaf hostname {
type inet:domain-name;
}
}
CBOR diagnostic notation: 1737
CBOR encoding: 19 06c9
*Second example:*
The following example shows the encoding of a leaf of type instance-
identifier which identify the data node instance
"/system/authentication/user/authorized-key/key-data" (SID 1730) for
user name "bob" and authorized-key "admin".
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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;
}
}
CBOR diagnostic notation: [1730, "bob", "admin"]
CBOR encoding:
83 # array(3)
19 06c2 # unsigned(1730)
63 # text(3)
626f62 # "bob"
65 # text(5)
61646d696e # "admin"
*Third example:*
The following example shows the encoding of a leaf of type instance-
identifier which identify the list instance "/system/authentication/
user" (SID 1726) corresponding to the user name "jack".
CBOR diagnostic notation: [1726, "jack"]
CBOR encoding:
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82 # array(2)
19 06be # unsigned(1726)
64 # text(4)
6a61636b # "jack"
5.13.2. Names as instance-identifier
The use of names as instance-identifier is defined in [RFC7951]
section 6.11. The resulting xpath MUST be encoded using a CBOR text
string data item (major type 3).
*First example:*
This example is described in Section 5.13.1.
CBOR diagnostic notation: "/ietf-system:system/contact"
CBOR encoding:
78 1c 2f20696574662d73797374656d3a73797374656d2f636f6e74616374
*Second example:*
This example is described in Section 5.13.1.
CBOR diagnostic notation:
"/ietf-system:system/authentication/user[name='bob']/authorized-key
[name='admin']/key-data"
CBOR encoding:
78 59
2f696574662d73797374656d3a73797374656d2f61757468656e74696361
74696f6e2f757365725b6e616d653d27626f62275d2f617574686f72697a
65642d6b65795b6e616d653d2761646d696e275d2f6b65792d64617461
*Third example:*
This example is described in Section 5.13.1.
CBOR diagnostic notation:
"/ietf-system:system/authentication/user[name='bob']"
CBOR encoding:
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78 33
2f696574662d73797374656d3a73797374656d2f61757468656e74696361
74696f6e2f757365725b6e616d653d27626f62275d
6. 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.
7. IANA Considerations
7.1. 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 |
+-----+---------------------+---------------------------+-----------+
| 40 | bits | YANG bits datatype | RFC XXXX |
| 41 | enumeration | YANG enumeration datatype | RFC XXXX |
| 42 | identityref | YANG identityref datatype | RFC XXXX |
| 43 | instance-identifier | YANG instance-identifier | RFC XXXX |
| | | datatype | |
+-----+---------------------+---------------------------+-----------+
// RFC Ed.: update Tag values using allocated tags if needed and
remove this note // RFC Ed.: replace XXXX with RFC number and remove
this note
8. 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].
[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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9. References
9.1. 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,
<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>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>.
9.2. Informative References
[I-D.ietf-core-sid]
Somaraju, A., Veillette, M., Pelov, A., Turner, R., and A.
Minaburo, "YANG Schema Item iDentifier (SID)", draft-ietf-
core-sid-00 (work in progress), October 2016.
[I-D.vanderstok-core-comi]
Stok, P., Bierman, A., Veillette, M., and A. Pelov, "CoAP
Management Interface", draft-vanderstok-core-comi-10 (work
in progress), October 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>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<http://www.rfc-editor.org/info/rfc7951>.
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
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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/
Ana Minaburo
Acklio
2bis rue de la chataigneraie
Cesson-Sevigne, Bretagne 35510
France
Email: ana@ackl.io
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