draft-bormann-cbor-notable-tags-02

draft-bormann-cbor-notable-tags-02
Internet-Draft
Notable CBOR Tags
June 2020
Bormann
Expires 27 December 2020
[Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-bormann-cbor-notable-tags-02
Published:
25 June 2020
Intended Status:
Informational
Expires:
27 December 2020
Author:
C. Bormann
Universität Bremen TZI
Notable CBOR Tags
Abstract
The Concise Binary Object Representation (CBOR, RFC 7049) is a data
format whose design goals include the possibility of extremely small
code size, fairly small message size, and extensibility without the
need for version negotiation.
In CBOR, one point of extensibility is the definition of CBOR tags.
RFC 7049 and its revision 7049bis define a basic set of tags as well
as a registry that can be used to contribute additional tag
definitions
IANA.cbor-tags
. Since RFC 7049 was published, some 80 tag
definitions have been added to that registry.
The present document provides a roadmap to a large subset of these tag
definitions. Where applicable, it points to a IETF standards or
standard development document
that specifies the tag. Where no such document exists, the intention
is to collect specification information from the sources of the
registrations. After some more development, the present document is
intended to be useful as a reference document for the IANA
registrations of the CBOR tags the definitions of which have been
collected.
Note to Readers
This is an individual submission to the CBOR working group of the
IETF,
Discussion currently takes places on the github repository
If the CBOR WG believes this is a useful document, discussion is
likely to move to the CBOR WG mailing list and a github repository at
the CBOR WG github organization,
The current version is true work in progress; some of the sections
haven't been filled in yet, and in particular, permission has not been
obtained from tag definition authors to copy over their text.
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
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 27 December 2020.
Copyright Notice
Copyright (c) 2020 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
) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
Table of Contents
1.
Introduction
(TO DO, expand on text from abstract here; move references here and
neuter them in the abstract as per Section 4.3 of
RFC7322
.)
The selection of the tags presented here is somewhat arbitrary;
considerations such as how wide the scope and area of application of a
tag definition is combine with an assessment how "ready to use" the
tag definition is (i.e., is the tag specification in a state where it
can be used).
This document can only be a snapshot of a subset of the current registrations.
The most up to date set of registrations is always available in the registry at
IANA.cbor-tags
1.1.
Terminology
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
RFC 2119
RFC2119
The definitions of
I-D.ietf-cbor-7049bis
apply.
The term "byte" is used in its now customary sense as a synonym for
"octet".
Where bit arithmetic is explained, this document uses the notation
familiar from the programming language C (including C++14's 0bnnn
binary literals), except that the operator "**" stands for
exponentiation.
2.
RFC 7049 (CBOR)
RFC7049
defines a number of tags that are listed here for
convenience only.
Table 1
Tag numbers defined in RFC 7049
Tag number
Tag content
Short Description
Section of RFC 7049
UTF-8 string
Standard date/time string
2.4.1
multiple
Epoch-based date/time
2.4.1
byte string
Positive bignum
2.4.2
byte string
Negative bignum
2.4.2
array
Decimal fraction
2.4.3
array
Bigfloat
2.4.3
21
multiple
Expected conversion to base64url encoding
2.4.4.2
22
multiple
Expected conversion to base64 encoding
2.4.4.2
23
multiple
Expected conversion to base16 encoding
2.4.4.2
24
byte string
Encoded CBOR data item
2.4.4.1
32
UTF-8 string
URI
2.4.4.3
33
UTF-8 string
base64url
2.4.4.3
34
UTF-8 string
base64
2.4.4.3
35
UTF-8 string
Regular expression
2.4.4.3
36
UTF-8 string
MIME message
2.4.4.3
55799
multiple
Self-describe CBOR
2.4.5
2.1.
Tags Related to Those Defined in RFC 7049
Separately registered tags that are directly related to the tags
predefined in RFC 7049 include:
Tag 63, registered by this document, is a parallel to tag 24, with
the single difference that its byte string tag content carries a
CBOR Sequence
RFC8742
instead of a single CBOR data items.
Tag 257, registered by Peter Occil with a specification in
, is a parallel to
tag 36, except that the tag content is a byte string, which
therefore can also carry binary MIME messages as per
RFC2045
3.
Security
A number of CBOR tags are defined in security specifications that make
use of CBOR.
3.1.
RFC 8152 (COSE)
RFC8152
defines CBOR Object Signing and Encryption (COSE).
A revision is in process that splits this specification into the data
structure definitions
I-D.ietf-cose-rfc8152bis-struct
, which will
define another tag for COSE standalone counter signature, and the
algorithms employed
I-D.ietf-cose-rfc8152bis-algs
Table 2
Tag numbers defined in RFC 8152, COSE
Tag number
Tag content
Short Description
16
COSE_Encrypt0
COSE Single Recipient Encrypted Data Object
17
COSE_Mac0
COSE Mac w/o Recipients Object
18
COSE_Sign1
COSE Single Signer Data Object
96
COSE_Encrypt
COSE Encrypted Data Object
97
COSE_Mac
COSE MACed Data Object
98
COSE_Sign
COSE Signed Data Object
3.2.
RFC 8392 (CWT)
RFC8392
defines the CBOR Web Token (CWT), making use of COSE to
define a CBOR variant of the JOSE Web Token (JWT),
RFC7519
, a
standardized security token that has found use
Table 3
Tag number defined for RFC 8392 CBOR Web Token (CWT)
Tag number
Tag content
Short Description
61
CBOR Web Token (CWT)
CBOR Web Token (CWT)
4.
CBOR-based Representation Formats
Representation formats can be built on top of CBOR.
4.1.
YANG-CBOR
YANG
RFC7950
is a data modeling language originally designed in
the context of the Network Configuration Protocol (NETCONF)
RFC6241
, now widely used for modeling management and
configuration information.
RFC7950
defines an XML-based
representation format, and
RFC7951
defines a JSON-based
RFC8259
representation format for YANG.
YANG-CBOR
I-D.ietf-core-yang-cbor
is a representation format for
YANG data in CBOR.
Table 4
Tag number defined for YANG-CBOR
Tag number
Tag content
Short Description
Section of YANG-CBOR
43
byte string
YANG bits datatype
6.7
44
unsigned integer
YANG enumeration datatype
6.6
45
unsigned integer or text string
YANG identityref datatype
6.10
46
unsigned integer or text string or array
YANG instance-identifier datatype
6.13
47
unsigned integer
YANG Schema Item iDentifier (sid)
3.2
5.
Protocols
Protocols may want to allocate CBOR tag numbers to identify specific
protocol elements.
5.1.
DOTS
DDoS Open Threat Signaling (DOTS) defines tag number 271 for the DOTS
signal channel object in
I-D.ietf-dots-signal-channel
5.2.
RAINS
As an example for how experimental protocols can make use of CBOR tag
definitions, the RAINS (Another Internet Naming Service) Protocol
Specification defines tag number 15309736 for a RAINS Message
I-D.trammell-rains-protocol
6.
Datatypes
6.1.
Advanced arithmetic
A number of tags have been registered for arithmetic representations
beyond those built into CBOR and defined by tags in
RFC7049
These are all documented under
; the
last pathname component is given in
Table 5
(TO DO: Obtain permission to copy the definitions here.)
Table 5
Tags for advanced arithmetic
Tag number
Tag content
Short Description
Reference
30
array
Rational number
rational.html
264
array
Decimal fraction with arbitrary exponent
bigfrac.html
265
array
Bigfloat with arbitrary exponent
bigfrac.html
268
array
Extended decimal fraction
extended.html
269
array
Extended bigfloat
extended.html
270
array
Extended rational number
extended.html
6.2.
Variants of undefined
defines tag 31 to be applied to the CBOR value Undefined (0xf7),
slightly modifying its semantics to stand for an absent value in a
CBOR Array.
(TO DO: Obtain permission to copy the definitions here.)
6.3.
Typed and Homogeneous Arrays
RFC8746
defines tags for various kinds of arrays. A summary is
reproduced in
Table 6
Table 6
Tag numbers defined for Arrays
Tag
Data Item
Semantics
64
byte string
uint8 Typed Array
65
byte string
uint16, big endian, Typed Array
66
byte string
uint32, big endian, Typed Array
67
byte string
uint64, big endian, Typed Array
68
byte string
uint8 Typed Array, clamped arithmetic
69
byte string
uint16, little endian, Typed Array
70
byte string
uint32, little endian, Typed Array
71
byte string
uint64, little endian, Typed Array
72
byte string
sint8 Typed Array
73
byte string
sint16, big endian, Typed Array
74
byte string
sint32, big endian, Typed Array
75
byte string
sint64, big endian, Typed Array
76
byte string
(reserved)
77
byte string
sint16, little endian, Typed Array
78
byte string
sint32, little endian, Typed Array
79
byte string
sint64, little endian, Typed Array
80
byte string
IEEE 754 binary16, big endian, Typed Array
81
byte string
IEEE 754 binary32, big endian, Typed Array
82
byte string
IEEE 754 binary64, big endian, Typed Array
83
byte string
IEEE 754 binary128, big endian, Typed Array
84
byte string
IEEE 754 binary16, little endian, Typed Array
85
byte string
IEEE 754 binary32, little endian, Typed Array
86
byte string
IEEE 754 binary64, little endian, Typed Array
87
byte string
IEEE 754 binary128, little endian, Typed Array
40
array of two arrays*
Multi-dimensional Array, row-major order
1040
array of two arrays*
Multi-dimensional Array, column-major order
41
array
Homogeneous Array
7.
Domain-Specific
(TO DO: Obtain permission to copy the definitions here; create proper table.)
37 byte string Binary UUID ([RFC4122] section [https://github.com/lucas-clemente/cbor-specs/blob/master/uuid.md][Lucas_Clemente]
4.1.2)
38 array Language-tagged string [http://peteroupc.github.io/CBOR/langtags.html][Peter_Occil]
257 byte string Binary MIME message [http://peteroupc.github.io/CBOR/binarymime.html][Peter_Occil]

260 byte string Network Address (IPv4 or IPv6 or [http://www.employees.org/~ravir/cbor-network.txt][Ravi_Raju]
MAC Address)
map Network Address Prefix (IPv4 or
261 (IPAddress + IPv6 Address + Mask Length) [https://github.com/toravir/CBOR-Tag-Specs/blob/master/networkPrefix.md][Ravi_Raju]
Mask Length)

263 byte string Hexadecimal string [https://github.com/toravir/CBOR-Tag-Specs/blob/master/hexString.md][Ravi_Raju]

266 text string Internationalized resource [https://peteroupc.github.io/CBOR/iri.html][Peter_Occil]
identifier (IRI)
Internationalized resource
267 text string identifier reference (IRI [https://peteroupc.github.io/CBOR/iri.html][Peter_Occil]
reference)
7.1.
Extended Time Formats
Additional tag definitions have been provided for date and time values.
Table 7
Tag numbers for date and time
Tag
Data Item
Semantics
Reference
100
integer
date in number of days since epoch
I-D.ietf-cbor-date-tag
1004
text string
RFC 3339 full-date string
I-D.ietf-cbor-date-tag
1001
map
extended time
I-D.bormann-cbor-time-tag
1002
map
duration
I-D.bormann-cbor-time-tag
1003
map
period
I-D.bormann-cbor-time-tag
TO DO: Wait for registration for 100 and 1004 to have completed.
8.
Platform-oriented
8.1.
Perl
(These are actually not as Perl-specific as the title of this section
suggests. See also the penultimate paragraph of Section 3.4 of
I-D.ietf-cbor-7049bis
.)
These are all documented under
; the
last pathname component is given in
Table 8
(TO DO: Obtain permission to copy the definitions here.)
Table 8
Tag numbers that aid the Perl platform
Tag
Data Item
Semantics
Reference
256
multiple
mark value as having string references
stringref
25
unsigned integer
reference the nth previously seen string
stringref
26
array
Serialised Perl object with classname and constructor arguments
perl-object
27
array
Serialised language-independent object with type name and constructor arguments
generic-object
28
multiple
mark value as (potentially) shared
value-sharing
29
unsigned integer
reference nth marked value
value-sharing
22098
multiple
hint that indicates an additional level of indirection
indirection
8.2.
JSON
(TO DO: Obtain permission to copy the definitions here.)
Tag number 262 has been registered to identify byte strings that carry embedded
JSON text (
).
Tag number 275 can be used to identify maps that contain keys that are
all of type Text String, as they would occur in JSON
).
8.3.
Weird text encodings
(TO DO: Obtain permission to copy the definitions here.)
Some variants of UTF-8 are in use in specific areas of application.
Tags have been registered to be able to carry around strings in these
variants in case they are not also valid UTF-8 and can therefore not
be represented as a CBOR text string
).
Table 9
Tag numbers for UTF-8 variants
Tag Number
Data Item
Semantics
272
byte string
Non-UTF-8 CESU-8 string
273
byte string
Non-UTF-8 WTF-8 string
274
byte string
Non-UTF-8 MUTF-8 string
9.
Application-specific
(TO DO: Obtain permission to copy the definitions here; create proper table.)
39 multiple Identifier [https://github.com/lucas-clemente/cbor-specs/blob/master/id.md][Lucas_Clemente]
42 byte string IPLD content identifier [https://github.com/ipld/cid-cbor/][Volker_Mische]

103 array Geographic Coordinates [https://github.com/allthingstalk/cbor/blob/master/CBOR-Tag103-Geographic-Coordinates.md][Danilo_Vidovic]
104 multiple Geographic Coordinate Reference [draft-clarke-cbor-crs]
System WKT or EPSG number

120 multiple Internet of Things Data Point [https://github.com/allthingstalk/cbor/blob/master/CBOR-Tag120-Internet-of-Things-Data-Points.md][Danilo_Vidovic]

258 array Mathematical finite set [https://github.com/input-output-hk/cbor-sets-spec/blob/master/CBOR_SETS.md][Alfredo_Di_Napoli]
Map datatype with key-value
259 map operations (e.g. [https://github.com/shanewholloway/js-cbor-codec/blob/master/docs/CBOR-259-spec--explicit-maps.md][Shane_Holloway]
`.get()/.set()/.delete()`)
10.
Implementation aids
10.1.
Invalid Tag
The present document registers tag numbers 65535, 4294967295, and
18446744073709551615 (16-bit 0xffff, 32-bit 0xffffffff, and 64-bit
0xffffffffffffffff) as Invalid Tags, tags that are always invalid,
independent of the tag content provided. The purpose of these tag
number registrations is to enable the tag numbers to be reserved for
internal use by implementations to note the absence of a tag on a data
item where a tag could also be expected with that data item as tag
content.
The Invalid Tags are not intended to ever occur in interchanged CBOR
data items. Generic CBOR decoder implementations are encouraged to
raise an error if an Invalid Tag occurs in a CBOR data item even if
there is no validity checking implemented otherwise.
11.
IANA Considerations
In the registry
IANA.cbor-tags
IANA has allocated the first to third tag in
Table 10
from the
FCFS space, with the present document as the specification reference.
IANA is requested to register the fourth tag from the Specification
Required space, with the present document as the specification reference.
Table 10
Values for Tags
Tag
Data Item
Semantics
Reference
65535
(none valid)
always invalid
draft-bormann-cbor-notable-tags,
Section 10.1
4294967295
(none valid)
always invalid
draft-bormann-cbor-notable-tags,
Section 10.1
18446744073709551615
(none valid)
always invalid
draft-bormann-cbor-notable-tags,
Section 10.1
63
byte string
Encoded CBOR Sequence
RFC8742
draft-bormann-cbor-notable-tags,
Section 2.1
12.
Security Considerations
The security considerations of RFC 7049 apply; the tags discussed here
may also have specific security considerations that are mentioned in
their specific sections above.
13.
References
13.1.
Normative References
[I-D.ietf-cbor-7049bis]
Bormann, C.
and P. Hoffman
"Concise Binary Object Representation (CBOR)"
Work in Progress
Internet-Draft, draft-ietf-cbor-7049bis-14
16 June 2020
[I-D.ietf-core-yang-cbor]
Veillette, M.
, Petrov, I.
, and A. Pelov
"CBOR Encoding of Data Modeled with YANG"
Work in Progress
Internet-Draft, draft-ietf-core-yang-cbor-12
9 March 2020
[I-D.ietf-dots-signal-channel]
Reddy.K, T.
, Boucadair, M.
, Patil, P.
, Mortensen, A.
, and N. Teague
"Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification"
Work in Progress
Internet-Draft, draft-ietf-dots-signal-channel-41
6 January 2020
[IANA.cbor-tags]
IANA
"Concise Binary Object Representation (CBOR) Tags"
[RFC2119]
Bradner, S.
"Key words for use in RFCs to Indicate Requirement Levels"
BCP 14
RFC 2119
DOI 10.17487/RFC2119
March 1997
[RFC7049]
Bormann, C.
and P. Hoffman
"Concise Binary Object Representation (CBOR)"
RFC 7049
DOI 10.17487/RFC7049
October 2013
[RFC8152]
Schaad, J.
"CBOR Object Signing and Encryption (COSE)"
RFC 8152
DOI 10.17487/RFC8152
July 2017
[RFC8392]
Jones, M.
, Wahlstroem, E.
, Erdtman, S.
, and H. Tschofenig
"CBOR Web Token (CWT)"
RFC 8392
DOI 10.17487/RFC8392
May 2018
[RFC8746]
Bormann, C., Ed.
"Concise Binary Object Representation (CBOR) Tags for Typed Arrays"
RFC 8746
DOI 10.17487/RFC8746
February 2020
13.2.
Informative References
[I-D.bormann-cbor-time-tag]
Bormann, C.
, Gamari, B.
, and H. Birkholz
"Concise Binary Object Representation (CBOR) Tags for Time, Duration, and Period"
Work in Progress
Internet-Draft, draft-bormann-cbor-time-tag-03
9 March 2020
[I-D.ietf-cbor-date-tag]
Jones, M.
, Nadalin, A.
, and J. Richter
"Concise Binary Object Representation (CBOR) Tags for Date"
Work in Progress
Internet-Draft, draft-ietf-cbor-date-tag-01
9 June 2020
[I-D.ietf-cose-rfc8152bis-algs]
Schaad, J.
"CBOR Object Signing and Encryption (COSE): Initial Algorithms"
Work in Progress
Internet-Draft, draft-ietf-cose-rfc8152bis-algs-09
2 June 2020
[I-D.ietf-cose-rfc8152bis-struct]
Schaad, J.
"CBOR Object Signing and Encryption (COSE): Structures and Process"
Work in Progress
Internet-Draft, draft-ietf-cose-rfc8152bis-struct-10
2 June 2020
[I-D.trammell-rains-protocol]
Trammell, B.
and C. Fehlmann
"RAINS (Another Internet Naming Service) Protocol Specification"
Work in Progress
Internet-Draft, draft-trammell-rains-protocol-05
29 January 2019
[RFC2045]
Freed, N.
and N. Borenstein
"Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies"
RFC 2045
DOI 10.17487/RFC2045
November 1996
[RFC4122]
Leach, P.
, Mealling, M.
, and R. Salz
"A Universally Unique IDentifier (UUID) URN Namespace"
RFC 4122
DOI 10.17487/RFC4122
July 2005
[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
[RFC7322]
Flanagan, H.
and S. Ginoza
"RFC Style Guide"
RFC 7322
DOI 10.17487/RFC7322
September 2014
[RFC7519]
Jones, M.
, Bradley, J.
, and N. Sakimura
"JSON Web Token (JWT)"
RFC 7519
DOI 10.17487/RFC7519
May 2015
[RFC7950]
Bjorklund, M., Ed.
"The YANG 1.1 Data Modeling Language"
RFC 7950
DOI 10.17487/RFC7950
August 2016
[RFC7951]
Lhotka, L.
"JSON Encoding of Data Modeled with YANG"
RFC 7951
DOI 10.17487/RFC7951
August 2016
[RFC8259]
Bray, T., Ed.
"The JavaScript Object Notation (JSON) Data Interchange Format"
STD 90
RFC 8259
DOI 10.17487/RFC8259
December 2017
[RFC8742]
Bormann, C.
"Concise Binary Object Representation (CBOR) Sequences"
RFC 8742
DOI 10.17487/RFC8742
February 2020
Acknowledgements
Contributors
Peter Occil
Email:
poccil14 at gmail dot com
Many More
To do
Author's Address
Carsten Bormann
Universität Bremen TZI
Postfach 330440
D-28359
Bremen
Germany
Phone:
+49-421-218-63921
Email:
cabo@tzi.org
Datatracker
draft-bormann-cbor-notable-tags-02
This is an older version of an Internet-Draft whose latest revision state is "Active".
Document
Document type
This is an older version of an Internet-Draft whose latest revision state is "Active".
Expired & archived
This document is an Internet-Draft (I-D).
Anyone may submit an I-D to the IETF.
This I-D is
not endorsed by the IETF
and has
no formal standing
in the
IETF standards process
Select version
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
Compare versions
Author
Carsten Bormann
RFC stream
(None)
Other formats
txt
html
xml
bibtex
bibxml
Report a datatracker bug
Show sidebar by default
Yes
No
Tab to show by default
Info
Contents
HTMLization configuration
HTMLize the plaintext
Plaintextify the HTML
Maximum font size
Page dependencies
Inline
Reference
Citation links
Go to reference section
Go to linked document