Uniform Resource Names for Device Identifiers

Document Type Active Internet-Draft (core WG)
Authors Jari Arkko  , Cullen Jennings  , Zach Shelby 
Last updated 2021-03-29 (latest revision 2021-02-22)
Replaces draft-arkko-core-dev-urn
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Network Working Group                                           J. Arkko
Internet-Draft                                                  Ericsson
Intended status: Standards Track                             C. Jennings
Expires: August 27, 2021                                           Cisco
                                                               Z. Shelby
                                                       February 23, 2021

             Uniform Resource Names for Device Identifiers


   This document describes a new Uniform Resource Name (URN) namespace
   for hardware device identifiers.  A general representation of device
   identity can be useful in many applications, such as in sensor data
   streams and storage, or equipment inventories.  A URN-based
   representation can be passed along in applications that need the

Status of This Memo

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

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   This Internet-Draft will expire on August 27, 2021.

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   Copyright (c) 2021 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
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   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.  Requirements language . . . . . . . . . . . . . . . . . . . .   4
   3.  DEV URN Definition  . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Purpose . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   5
       3.2.1.  Character Case and URN-Equivalence  . . . . . . . . .   6
     3.3.  Assignment  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.4.  Security and Privacy  . . . . . . . . . . . . . . . . . .   7
     3.5.  Interoperability  . . . . . . . . . . . . . . . . . . . .   7
     3.6.  Resolution  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.7.  Documentation . . . . . . . . . . . . . . . . . . . . . .   7
     3.8.  Additional Information  . . . . . . . . . . . . . . . . .   8
     3.9.  Revision Information  . . . . . . . . . . . . . . . . . .   8
   4.  DEV URN Subtypes  . . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  MAC Addresses . . . . . . . . . . . . . . . . . . . . . .   8
     4.2.  1-Wire Device Identifiers . . . . . . . . . . . . . . . .   8
     4.3.  Organization-Defined Identifiers  . . . . . . . . . . . .   9
     4.4.  Organization Serial Numbers . . . . . . . . . . . . . . .   9
     4.5.  Organization Product and Serial Numbers . . . . . . . . .  10
     4.6.  Future Subtypes . . . . . . . . . . . . . . . . . . . . .  10
   5.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
     6.1.  Privacy . . . . . . . . . . . . . . . . . . . . . . . . .  12
     6.2.  Validity  . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  Changes from Previous Versions . . . . . . . . . . .  16
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   This document describes a new Uniform Resource Name (URN) [RFC8141]
   namespace for hardware device identifiers.  A general representation
   of device identity can be useful in many applications, such as in
   sensor data streams and storage [RFC8428], or equipment inventories
   [RFC7252], [I-D.ietf-core-resource-directory].

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   A URN-based representation can be passed along in applications that
   need the information.  It fits particularly well for protocols
   mechanisms that are designed to carry URNs [RFC7230], [RFC7540],
   [RFC3261], [RFC7252].  Finally, URNs can also be easily carried and
   stored in formats such as XML [W3C.REC-xml-19980210], JSON [RFC8259]
   or SenML [RFC8428].  Using URNs in these formats is often preferable
   as they are universally recognized and self-describing, and therefore
   avoid the need for agreeing to interpret an octet string as a
   specific form of a MAC address, for instance.  Passing URNs may
   consume additional bytes compared to, for instance, passing 4-byte
   binary IPv4 addresses, but offers some flexibility in return.

   This document defines identifier URN types for situations where no
   such convenient type already exists.  For instance, [RFC6920] defines
   cryptographic identifiers, [RFC7254] defines International Mobile
   station Equipment Identity (IMEI) identifiers for use with 3GPP
   cellular systems, and [RFC8464] defines Mobile Equipment Identity
   (MEID) identifiers for use with 3GPP2 cellular systems.  Those URN
   types should be employed when such identifiers are transported; this
   document does not redefine these identifiers in any way.

   Universally Unique IDentifier (UUID) URNs [RFC4122] are another
   alternative way for representing device identifiers, and already
   support MAC addresses as one type of an identifier.  However, UUIDs
   can be inconvenient in environments where it is important that the
   identifiers are as simple as possible and where additional
   requirements on stable storage, real-time clocks, and identifier
   length can be prohibitive.  Often, UUID-based identifiers are
   preferred for general purpose uses instead of MAC-based device URNs
   defined in this document.  The device URNs are recommended for
   constrained environments.

   Future device identifier types can extend the device URN type defined
   here (see Section 7), or define their own URNs.

   Note that long-term stable unique identifiers are problematic for
   privacy reasons and should be used with care as described in

   The rest of this document is organized as follows.  Section 3 defines
   the "DEV" URN type, and Section 4 defines subtypes for IEEE MAC-48,
   EUI-48 and EUI-64 addresses and 1-Wire device identifiers.  Section 5
   gives examples.  Section 6 discusses the security and privacy
   considerations of the new URN type.  Finally, Section 7 specifies the
   IANA registration for the new URN type and sets requirements for
   subtype allocations within this type.

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2.  Requirements language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  DEV URN Definition

   Namespace Identifier: "dev" requested

   Version: 1

   Date: 2020-06-24

   Registrant: IETF and the CORE working group.  Should the working
   group cease to exist, discussion should be directed to the
   application area or general IETF discussion forums, or the IESG.

3.1.  Purpose

   Purpose: The DEV URNs identify devices with device-specific
   identifiers such as network card hardware addresses.  DEV URNs are
   scoped to be globally applicable (see [RFC8141] Section 6.4.1) and,
   in general, enable systems to use these identifiers from multiple
   sources in an interoperable manner.  Note that in some deployments,
   ensuring uniqueness requires care if manual or local assignment
   mechanisms are used, as discussed in Section 3.3.

   Some typical DEV URN applications include equipment inventories and
   smart object systems.

   DEV URNs can be used in various ways in applications, software
   systems, and network components, in tasks ranging from discovery (for
   instance when discovering 1-Wire network devices or detecting MAC-
   addressable devices on a LAN) to intrusion detection systems and
   simple catalogues of system information.

   While it is possible to implement resolution systems for specific
   applications or network locations, DEV URNs are typically not used in
   a way that requires resolution beyond direct observation of the
   relevant identifier fields in local link communication.  However, it
   is often useful to be able to pass device identifier information in
   generic URN fields in databases or protocol fields, which makes the
   use of URNs for this purpose convenient.

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   The DEV URN name space complements existing name spaces such as those
   involving IMEI or UUID identifiers.  DEV URNs are expected to be a
   part of the IETF-provided basic URN types, covering identifiers that
   have previously not been possible to use in URNs.

3.2.  Syntax

   Syntax: The identifier is expressed in ASCII characters and has a
   hierarchical structure as follows:

  devurn = "urn:dev:" body componentpart
  body = macbody / owbody / orgbody / osbody / opsbody / otherbody
  macbody = %s"mac:" hexstring
  owbody = %s"ow:" hexstring
  orgbody = %s"org:" posnumber "-" identifier *( ":"  identifier )
  osbody = %s"os:" posnumber "-" serial *( ":"  identifier )
  opsbody = %s"ops:" posnumber "-" product "-" serial *( ":"  identifier )
  otherbody = subtype ":" identifier *( ":"  identifier )
  subtype = LALPHA *(DIGIT / LALPHA)
  identifier = 1*devunreserved
  identifiernodash = 1*devunreservednodash
  product = identifiernodash
  serial = identifier
  componentpart = *( "_" identifier )
  devunreservednodash = ALPHA / DIGIT / "."
  devunreserved = devunreservednodash / "-"
  hexstring = 1*(hexdigit hexdigit)
  hexdigit = DIGIT / "a" / "b" / "c" / "d" / "e" / "f"
  posnumber = NZDIGIT *DIGIT
  ALPHA =  %x41-5A / %x61-7A
  LALPHA =  %x41-5A
  NZDIGIT = %x31-39
  DIGIT =  %x30-39

   The above syntax is represented in Augmented Backus-Naur Form (ABNF)
   form as defined in [RFC5234] and [RFC7405].  The syntax also copies
   the DIGIT and ALPHA rules originally defined in [RFC5234], exactly as
   defined there.

   The device identifier namespace includes five subtypes (see
   Section 4, and more may be defined in the future as specified in
   Section 7.

   The optional underscore-separated components at the end of the DEV
   URN depict individual aspects of a device.  The specific strings and
   their semantics are up to the designers of the device, but could be
   used to refer to specific interfaces or functions within the device.

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   With the exception of the MAC-address and 1-Wire DEV URNs, each DEV
   URN may also contain optional colon-separated identifiers.  These are
   provided for extensibility.

   There are no special character encoding rules or considerations for
   conforming with the URN syntax, beyond those applicable for URNs in
   general [RFC8141], or the context where these URNs are carried (e.g.,
   inside JSON [RFC8259] or SenML [RFC8428]).  Due to the SenML RFC 8428
   Section 4.5.1 rules, it is not desirable to use percent-encoding in
   DEV URNs, and the subtypes defined in this specification do not
   really benefit from percent-encoding.  However, this specification
   does not deviate from the general syntax of URNs or their processing
   and normalization rules as specified in [RFC3986] and [RFC8141].

   DEV URNs do not use r-, q-, or f-components as defined in [RFC8141].

   Specific subtypes of DEV URNs may be validated through mechanisms
   discussed in Section 4.

   The string representation of the device identifier URN is fully
   compatible with the URN syntax.

3.2.1.  Character Case and URN-Equivalence

   The DEV URN syntax allows both upper and lower case characters.  The
   URN-equivalence of the DEV URNs is defined per [RFC8141] Section 3.1,
   i.e., two URNs are URN-equivalent if their assigned-name portions are
   octet-by-octet equal after applying case normalization to the URI
   scheme ("urn") and namespace identifier ("dev").  The rest of the DEV
   URN is compared in a case sensitive manner.  It should be noted that
   URN-equivalence matching merely quickly shows that two URNs are
   definitely the same for the purposes of caching and other similar
   uses.  Two DEV URNs may still refer to the same entity, and not be
   found URN-equivalent according to the RFC 8141 definition.  For
   instance, in ABNF, strings are case-insensitive (see [RFC5234]
   Section 2.3), and a MAC address could be represented either with
   uppercase or lowercase hexadecimal digits.

   Character case is not otherwise significant for the DEV URN subtypes
   defined in this document.  However, future subtypes might include
   identifiers that use encodings such as BASE64, which encode strings
   in a larger variety of characters, and might even encode binary data.

   To facilitate equivalence checks, it is RECOMMENDED that
   implementations always use lower case letters where they have a
   choice in case, unless there is a reason otherwise.  (Such a reason
   might be, for instance, the use of a subtype that requires the use of
   both upper case and lower case letters.)

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3.3.  Assignment

   Assignment: The process for identifier assignment is dependent on the
   used subtype, and documented in the specific subsection under
   Section 4.

   Device identifiers are generally expected to identify a unique
   device, barring the accidental issue of multiple devices with the
   same identifiers.  In many cases, device identifiers can also be
   changed by users, or sometimes assigned in an algorithmic or local
   fashion.  Any potential conflicts arising from such assignments are
   not something that the DEV URNs as such manage; they simply are there
   to refer to a particular identifier.  And of course, a single device
   may (and often does) have multiple identifiers, e.g., identifiers
   associated with different link technologies it supports.

   The DEV URN type SHOULD only be used for hardware-based identifiers
   that are expected to be persistent (with some limits, as discussed

3.4.  Security and Privacy

   Security and Privacy: As discussed in Section 6, care must be taken
   in the use of device-identifier-based identifiers due to their nature
   as long-term identifiers that are not normally changeable.  Leakage
   of these identifiers outside systems where their use is justified
   should be controlled.

3.5.  Interoperability

   Interoperability: There are no specific interoperability concerns.

3.6.  Resolution

   Resolution: The device identifiers are not expected to be globally
   resolvable.  No identifier resolution system is expected.  Systems
   may perform local matching of identifiers to previously seen
   identifiers or configured information, however.

3.7.  Documentation

   See RFC NNNN (RFC Editor: Please replace NNNN by a reference to the
   RFC number of this document).

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3.8.  Additional Information

   See Section 1 for a discussion of related name spaces.

3.9.  Revision Information

   Revision Information: This is the first version of this registration.

4.  DEV URN Subtypes

4.1.  MAC Addresses

   DEV URNs of the "mac" subtype are based on the EUI-64 identifier
   [IEEE.EUI64] derived from a device with a built-in 64-bit EUI-64.
   The EUI-64 is formed from 24 or 36 bits of organization identifier
   followed by 40 or 28 bits of device-specific extension identifier
   assigned by that organization.

   In the DEV URN "mac" subtype the hexstring is simply the full EUI-64
   identifier represented as a hexadecimal string.  It is always exactly
   16 characters long.

   MAC-48 and EUI-48 identifiers are also supported by the same DEV URN
   subtype.  To convert a MAC-48 address to an EUI-64 identifier, The
   OUI of the MAC-48 address (the first three octets) becomes the
   organization identifier of the EUI-64 (the first three octets).  The
   fourth and fifth octets of the EUI are set to the fixed value 0xffff
   (hexadecimal).  The last three octets of the MAC-48 address become
   the last three octets of the EUI-64.  The same process is used to
   convert an EUI-48 identifier, but the fixed value 0xfffe is used

   Identifier assignment for all of these identifiers rests within the
   IEEE Registration Authority.

   Note that where randomized MAC addresses are used, the resulting DEV
   URNs cannot be expected to have uniqueness, as discussed in
   Section 3.3.

4.2.  1-Wire Device Identifiers

   The 1-Wire* system is a device communications bus system designed by
   Dallas Semiconductor Corporation. 1-Wire devices are identified by a
   64-bit identifier that consists of 8 bit family code, 48 bit
   identifier unique within a family, and 8 bit CRC code [OW].

      *) 1-Wire is a registered trademark.

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   In DEV URNs with the "ow" subtype the hexstring is a representation
   of the full 64-bit identifier as a hexadecimal string.  It is always
   exactly 16 characters long.  Note that the last two characters
   represent the 8-bit CRC code.  Implementations MAY check the validity
   of this code.

   Family code and identifier assignment for all 1-Wire devices rests
   with the manufacturers.

4.3.  Organization-Defined Identifiers

   Device identifiers that have only a meaning within an organization
   can also be used to represent vendor-specific or experimental
   identifiers or identifiers designed for use within the context of an

   Organizations are identified by their Private Enterprise Number (PEN)
   [RFC2578].  These numbers can be obtained from IANA.  Current PEN
   assignments can be viewed at https://www.iana.org/assignments/
   enterprise-numbers/enterprise-numbers and new assignments requested
   at https://pen.iana.org/pen/PenApplication.page.

   Note that when included in an "org" DEV URN, the number can not be
   zero or have leading zeroes, as the ABNF requires the number to start
   with a non-zero digit.

4.4.  Organization Serial Numbers

   The "os" subtype specifies an organization and a serial number.
   Organizations are identified by their PEN.  As with the organization-
   defined identifiers (Section 4.3), PEN number assignments are
   maintained by IANA, and assignments for new organizations can be made

      Historical note: The "os" subtype was originally been defined in
      the Open Mobile Alliance "Lightweight Machine to Machine" standard
      [LwM2M], but has been incorporated here to collect all syntax
      associated with DEV URNs in one place.  At the same time, the
      syntax of this subtype was changed to avoid the possibility of
      characters that are not allowed in SenML Name field (see [RFC8428]
      Section 4.5.1).

   Organization serial number DEV URNs consist of the PEN number and the
   serial number.  As with other DEV URNs, for carrying additional
   information and extensibility, optional colon-separated identifiers
   and underscore-separated components may also be included.  The serial
   numbers themselves are defined by the organization, and this
   specification does not specify how they are allocated.

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   Organizations are also encouraged to select serial number formats
   that avoid possibility for ambiguity, in the form of leading zeroes
   or otherwise.

4.5.  Organization Product and Serial Numbers

   The DEV URN "ops" subtype has originally been defined in the LwM2M
   standard, but has been incorporated here to collect all syntax
   associated with DEV URNs in one place.  The "ops" subtype specifies
   an organization, product class, and a serial number.  Organizations
   are identified by their PEN.  Again, as with the organization-defined
   identifiers (Section 4.3), PEN number assignments are maintained by

      Historical note: As with the "os" subtype, the "ops" subtype has
      originally been defined in OMA.

   Organization product and serial number DEV URNs consist of the PEN
   number, product class, and the serial number.  As with other DEV
   URNs, for carrying additional information and extensibility, optional
   colon-separated identifiers and underscore-separated components may
   also be included.  Both the product class and serial numbers
   themselves are defined by the organization, and this specification
   does not specify how they are allocated.

   Organizations are also encouraged to select product and serial number
   formats that avoid possibility for ambiguity.

4.6.  Future Subtypes

   Additional subtypes may be defined in other, future specifications.
   See Section 7.

   The DEV URN "example" subtype is reserved for use in examples.  It
   has no specific requirements beyond those expressed by the ABNF in
   Section 3.2.

5.  Examples

   The following provides some examples of DEV URNs:

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    urn:dev:mac:0024beffff804ff1            # The MAC-48 address of
                                            # 0024be804ff1, converted
                                            # to EUI-64 format

    urn:dev:mac:0024befffe804ff1            # The EUI-48 address of
                                            # 0024be804ff1, converted
                                            # to EUI-64 format

    urn:dev:mac:acde48234567019f            # The EUI-64 address of
                                            # acde48234567019f

    urn:dev:ow:10e2073a01080063             # A 1-Wire temperature
                                            # sensor

    urn:dev:ow:264437f5000000ed_humidity    # The humidity
                                            # part of a multi-sensor
                                            # device

    urn:dev:ow:264437f5000000ed_temperature # The temperature
                                            # part of a multi-sensor
                                            # device

    urn:dev:org:32473-foo                   # An organization-
                                            # specific URN in
                                            # the RFC 5612 example
                                            # organization, 32473.

    urn:dev:os:32473-123456                 # Device 123456 in
                                            # the RFC 5612 example
                                            # organization

    urn:dev:os:32473-12-34-56               # A serial number with
                                            # dashes in it

    urn:dev:ops:32473-Refrigerator-5002     # Refrigerator serial
                                            # number 5002 in the
                                            # RFC 5612 example
                                            # organization

    urn:dev:example:new-1-2-3_comp          # An example of something
                                            # that is not defined today,
                                            # and is not one of the
                                            # mac, ow, os, or ops
                                            # subtypes

   The DEV URNs themselves can then appear in various contexts.  A
   simple example of this is the use of DEV URNs in SenML data.  For

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   example, this example from [RFC8428] shows a measurement from a
   1-Wire temperature gauge encoded in the JSON syntax.


6.  Security Considerations

   On most devices, the user can display device identifiers.  Depending
   on circumstances, device identifiers may or may not be modified or
   tampered with by the user.  An implementation of the DEV URN MUST
   preserve such limitations and behaviors associated with the device
   identifiers.  In particular, a device identifier that is intended to
   be immutable should not become mutable as a part of implementing the
   DEV URN type.  More generally, nothing in this document should be
   construed to override what the relevant device specifications have
   already said about the identifiers.

6.1.  Privacy

   Other devices in the same network may or may not be able to identify
   the device.  For instance, on an Ethernet network, the MAC address of
   a device is visible to all other devices.

   DEV URNs often represent long-term stable unique identifiers for
   devices.  Such identifiers may have privacy and security implications
   because they may enable correlating information about a specific
   device over a long period of time, location tracking, and device
   specific vulnerability exploitation [RFC7721].  Also, in some systems
   there is no easy way to change the identifier.  Therefore these
   identifiers need to be used with care and especially care should be
   taken to avoid leaking them outside of the system that is intended to
   use the identifiers.

6.2.  Validity

   Information about identifiers may have significant effects in some
   applications.  For instance, in many sensor systems the identifier
   information is used for deciding how to use the data carried in a
   measurement report.  On some other systems, identifiers may be used
   in policy decisions.

   It is important that systems are designed to take into account the
   possibility of devices reporting incorrect identifiers (either
   accidentally or maliciously) and the manipulation of identifiers in
   communications by illegitimate entities.  Integrity protection of

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   communications or data objects, the use of trusted devices, and
   various management practices can help address these issues.

   The advice from [RFC4122] Section 6 also applies: Do not assume that
   DEV URNs are hard to guess.

7.  IANA Considerations

   This document requests the registration of a new URN namespace for
   "DEV", as described in Section 3.

   IANA is asked to create a "DEV URN Subtypes" registry.  The initial
   values in this registry are as follows:

Subtype  Description                              Reference
mac      MAC Addresses                            (THIS RFC) Section 4.1
ow       1-Wire Device Identifiers                (THIS RFC) Section 4.2
org      Organization-Defined Identifiers         (THIS RFC) Section 4.3
os       Organization Serial Numbers              (THIS RFC) Section 4.4
ops      Organization Product and Serial Numbers  (THIS RFC) Section 4.5
example  Reserved for examples                    (THIS RFC) Section 4.6

   Additional subtypes for DEV URNs can be defined through Specification
   Required or IESG Approval [RFC8126].  These allocations are
   appropriate when there is a new namespace of some type of device
   identifiers, defined in stable fashion and with a publicly available

   Note that the organization (Section 4.3) device identifiers can also
   be used in some cases, at least as a temporary measure.  It is
   preferable, however, that long-term usage of a broadly employed
   device identifier be registered with IETF rather than used through
   the organization device identifier type.

8.  References

8.1.  Normative References

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

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   [RFC2578]  McCloghrie, K., Ed., Perkins, D., Ed., and J.
              Schoenwaelder, Ed., "Structure of Management Information
              Version 2 (SMIv2)", STD 58, RFC 2578,
              DOI 10.17487/RFC2578, April 1999, <https://www.rfc-

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008, <https://www.rfc-

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,

   [RFC8141]  Saint-Andre, P. and J. Klensin, "Uniform Resource Names
              (URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

              IEEE, "Guidelines For 64-bit Global Identifier (EUI-64)",
              IEEE  , unknown year,

   [OW]       Maxim, "Guide to 1-Wire Communication", MAXIM
              documents/tutorials/1/1796.html, June 2008,

8.2.  Informative References

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002, <https://www.rfc-

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   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005, <https://www.rfc-

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,

   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015, <https://www.rfc-

   [RFC7721]  Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
              Considerations for IPv6 Address Generation Mechanisms",
              RFC 7721, DOI 10.17487/RFC7721, March 2016,

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017, <https://www.rfc-

              Sperberg-McQueen, C., Bray, T., and J. Paoli, "XML 1.0
              Recommendation", World Wide Web Consortium FirstEdition
              REC-xml-19980210, February 1998,

   [OUI]      IEEE, SA., "Registration Authority", IEEE-SA webpage,
              2018, <http://standards.ieee.org/develop/regauth/oui/>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014, <https://www.rfc-

   [RFC8428]  Jennings, C., Shelby, Z., Arkko, J., Keranen, A., and C.
              Bormann, "Sensor Measurement Lists (SenML)", RFC 8428,
              DOI 10.17487/RFC8428, August 2018, <https://www.rfc-

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   [RFC6920]  Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B.,
              Keranen, A., and P. Hallam-Baker, "Naming Things with
              Hashes", RFC 6920, DOI 10.17487/RFC6920, April 2013,

   [RFC7254]  Montemurro, M., Ed., Allen, A., McDonald, D., and P.
              Gosden, "A Uniform Resource Name Namespace for the Global
              System for Mobile Communications Association (GSMA) and
              the International Mobile station Equipment Identity
              (IMEI)", RFC 7254, DOI 10.17487/RFC7254, May 2014,

   [RFC7405]  Kyzivat, P., "Case-Sensitive String Support in ABNF",
              RFC 7405, DOI 10.17487/RFC7405, December 2014,

   [RFC8464]  Atarius, R., "A URN Namespace for Device Identity and
              Mobile Equipment Identity (MEID)", RFC 8464,
              DOI 10.17487/RFC8464, September 2018, <https://www.rfc-

              Amsuess, C., Shelby, Z., Koster, M., Bormann, C., and P.
              Stok, "CoRE Resource Directory", draft-ietf-core-resource-
              directory-26 (work in progress), November 2020.

   [LwM2M]    "OMA Lightweight Machine to Machine Requirements", OMA
              Standard Candidate Version 1.2, January 2019.

Appendix A.  Changes from Previous Versions

   Editor's note: Please remove this section before publication.

   Version -11 was created to address non-blocking comments from the
   IESG review.  This version made the following changes:

   o  Removed space after the "%s" in the ABNF RFC 7405 syntax.

   o  Softened and clarified the recommendation regarding UUIDs in
      Section 1.

   o  Added a paragraph about the impacts of using randomized MAC

   o  Added advice regarding ease of guessing DEV URNs, in Section 6.2.

   o  Simplified and clarified the "illegitimate entities" statement in
      Section 6.2.

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   o  Clarified the persistence statement in Section 3.3.

   Version -10 made the following changes:

   o  Restricted the case of "mac", "ow", etc. any subtype to lower
      case.  This required the adoption of RFC 7405 syntax in the ABNF.

   o  Added a reserved "example" subtype to be used in examples.

   o  Clarified global applicability, particularly in cases with local
      or manual assignment mechanisms.

   o  Corrected byte/bit counts in for 1-Wire identifiers in
      Section 4.2.

   o  Clarified that optional underscore-separated components come at
      the end of the DEV URN, not just "after the hexstring".

   o  Changed the requirement to not use percent-encoding to a
      preference instead of a hard rule, based on the needs of SenML but
      not wishing to break rules of RFC 8141.

   o  Added a description of tradeoffs involving using URNs instead of
      some more compact but more specific formats, in Section 1.

   o  Several minor corrections to the names in the ABNF.

   o  Added a reference for Base64 for clarity.

   o  Made the history of the OS and OPS subtypes a part of the
      permanent text, rather than an editor's note.

   o  Updated the 1-Wire reference URL.

   o  Some editorial corrections.

   Version -09 of the WG draft took into account IANA, SECDIR, Gen-ART,
   and OPSDIR reviews.  The following changes were made:

   o  Aligned the use of identifiers vs. identity terms.

   o  Added a security considerations subsection on validity of claimed

   o  Focused on "care" in the RFC 7721 reference, rather than "care and

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   o  Renamed the "unreserved" ABNF terminal to avoid confusion with the
      general URN ABNF terminal with the same name.

   o  Removed the mistakenly included text about MEID subtype.

   o  Clarified URN syntax differences and normalization rules wrt the
      lack of percent-encoding in DEV URNs.

   o  Required PEN numbers to start with non-zero digit in the ABNF and
      changed the associated language later in the draft.

   o  Text about case-insensitivity in RFC 5234 was clarified.

   o  Text about uniqueness was clarified.

   o  Text about global scope was clarified.

   o  An example of DEV URN usage in SenML was added.

   o  Editorial changes.

   Version -08 of the WG draft took into account Barry Leiba's AD review
   comments.  To address these comments, changes were made in

   o  Further updates of the upper/lower case rules for the DEV URNs.

   o  Further updates to the ABNF.

   o  The use of HEXDIG from RFC 5234.

   o  IANA considerations for the creation of separate registry for the
      own parameters of DEV URNs.

   o  Editorial improvements.

   Version -07 of the WG draft took into account Carsten Bormann's
   feedback, primarily on character case issues and editorials.

   Version -06 of the WG draft took into account Marco Tiloca's feedback
   before a second WGLC, primarily on further cleanup of references and
   editorial issues.

   Version -05 of the WG draft made some updates based on WGLC input:
   examples for MAC-48 and EUI-48, clarification with regards to leading
   zeroes, new recommendation with the use of lower-case letters to
   avoid comparison problems, small update of the RFC 8141 template
   usage, reference updates, and editorial corrections.

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   Version -04 of the WG draft cleaned up the ABNF:

   o  Parts of the ANBF now allow for use cases for the component part
      that were not previously covered: the syntax now allows the
      character "." to appear, and serial numbers can have dashes in

   o  The syntax was also extended to allow for extensibility by adding
      additional ":" separated parts for the org, op, ops, and other

   o  The ABNF was changed to include directly the ALPHA and DIGIT parts
      imported from RFC 5234, instead of just having a verbal comment
      about it.  (Note that the style in existing RFCs differs on this.)

   In addition, in -04 the MAC example was corrected to use the inserted
   value ffff instead of fffe, required by Section 4.1, the org example
   was corrected, the os: examples and otherbody examples were added.
   The IANA rules for allocating new subtypes was slightly relaxed in
   order to cover for new subtype cases that are brought up regularly,
   and often not from inside the IETF.  Finally, the allocation of PEN
   numbers and the use of product classes and serial numbers was better

   Version -03 of the WG draft removed some unnecessary references,
   updated some other references, removed pct-encoding to ensure the DEV
   URNs fit [RFC8428] Section 4.5.1 rules, and clarified that the
   original source of the "os" and "ops" subtypes.

   Version -02 of the WG draft folded in the "ops" and "os" branches of
   the dev:urn syntax from LwM2M, as they seemed to match well what
   already existed in this document under the "org" branch.  However, as
   a part of this three changes were incorporated:

   o  The syntax for the "org:" changes to use "-" rather than ":"
      between the OUI and the rest of the URN.

   o  The organizations for the "ops" and "os" branches have been
      changed to use PEN numbers rather than OUI numbers [OUI].  The
      reason for this is that PEN numbers are allocated through a
      simpler and less costly process.  However, this is a significant
      change to how LwM2M identifiers were specified before.

   o  There were also changes to what general characters can be used in
      the otherbody branch of the ABNF.

   The rationale for all these changes is that it would be helpful for
   the community collect and unify syntax between the different uses of

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   DEV URNs.  If there is significant use of either the org:, os:, or
   ops: subtypes, then changes at this point may not be warranted, but
   otherwise unified syntax, as well as the use of PEN numbers would
   probably be beneficial.  Comments on this topic are appreciated.

   Version -01 of the WG draft converted the draft to use the new URN
   registration template from [RFC8141].

   Version -00 of the WG draft renamed the file name and fixed the ABNF
   to correctly use "org:" rather than "dn:".

   Version -05 made a change to the delimiter for parameters within a
   DEV URN.  Given discussions on allowed character sets in SenML
   [RFC8428], we would like to suggest that the "_" character be used
   instead of ";", to avoid the need to translate DEV URNs in SenML-
   formatted communications or files.  However, this reverses the
   earlier decision to not use unreserved characters.  This also means
   that device IDs cannot use "_" characters, and have to employ other
   characters instead.  Feedback on this decision is sought.

   Version -05 also introduced local or organization-specific device
   identifiers.  Organizations are identified by their PEN number
   (although we considered FQDNs as a potential alternative.  The
   authors belive an organization-specific device identifier type will
   make experiments and local use easier, but feedback on this point and
   the choice of PEN numbers vs. other possible organization identifiers
   would be very welcome.

   Version -05 also added some discussion of privacy concerns around
   long-term stable identifiers.

   Finally, version -05 clarified the situations when new allocations
   within the registry of possible device identifier subtypes is

   Version -04 is a refresh, as the need and interest for this
   specification has re-emerged.  And the editing author has emerged
   back to actual engineering from the depths of IETF administration.

   Version -02 introduced several changes.  The biggest change is that
   with the NI URNs [RFC6920], it was no longer necessary to define
   cryptographic identifiers in this specification.  Another change was
   that we incorporated a more generic syntax for future extensions;
   non-hexstring identifiers can now also be supported, if some future
   device identifiers for some reason would, for instance, use some kind
   of encoding such as Base64 [RFC4648].  As a part of this change, we
   also changed the component part separator character from '-' to ';'

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   so that the general format of the rest of the URN can employ the
   unreserved characters [RFC3986].

   Version -03 made several minor corrections to the ABNF as well as
   some editorial corrections.

Appendix B.  Acknowledgments

   The authors would like to thank Ari Keranen, Stephen Farrell,
   Christer Holmberg, Peter Saint-Andre, Wouter Cloetens, Jaime Jimenez,
   Joseph Knapp, Padmakumar Subramani, Mert Ocak, Hannes Tschofenig, Jim
   Schaad, Thomas Fossati, Carsten Bormann, Marco Tiloca, Barry Leiba,
   Amanda Baber, Juha Hakala, Dale Worley, Warren Kumari, Benjamin
   Kaduk, Brian Weis, John Klensin, Dave Thaler, Russ Housley, Dan
   Romascanu, Eric Vyncke, Roman Danyliw, and Ahmad Muhanna for feedback
   and interesting discussions in this problem space.  We would also
   like to note prior documents that focused on specific device
   identifiers, such as [RFC7254] or [RFC8464].

Authors' Addresses

   Jari Arkko
   Jorvas  02420

   Email: jari.arkko@piuha.net

   Cullen Jennings
   170 West Tasman Drive
   San Jose, CA  95134

   Phone: +1 408 421-9990
   Email: fluffy@cisco.com

   Zach Shelby
   Kidekuja 2
   Vuokatti  88600

   Phone: +358407796297
   Email: Zach.Shelby@arm.com

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