Network Working Group                                           J. Arkko
Internet-Draft                                                  Ericsson
Intended status: Informational                               C. Jennings
Expires: May 3, 2012                                               Cisco
                                                               Z. Shelby
                                                        October 31, 2011

             Uniform Resource Names for Device Identifiers


   This memo 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 easily passed along in any application that
   needs the information.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 3, 2012.

Copyright Notice

   Copyright (c) 2011 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

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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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements language  . . . . . . . . . . . . . . . . . . . .  4
   3.  DEV URN Definition . . . . . . . . . . . . . . . . . . . . . .  4
   4.  DEV URN Subtypes . . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  MAC Addresses  . . . . . . . . . . . . . . . . . . . . . .  5
     4.2.  1-Wire Device Identifiers  . . . . . . . . . . . . . . . .  6
     4.3.  Cryptographically Generated Identifiers  . . . . . . . . .  6
   5.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  8
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  8
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10

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1.  Introduction

   This memo describes a new Uniform Resource Name (URN) [RFC2141]
   [RFC3406] 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
   [I-D.ietf-core-coap], [I-D.jennings-senml],
   [I-D.arkko-core-sleepy-sensors] [I-D.arkko-core-security-arch].  A
   URN-based representation can be easily passed along in any
   application that needs the information, as it fits in protocols
   mechanisms that are designed to carry URNs [RFC2616], [RFC3261],
   [I-D.ietf-core-coap].  Finally, URNs can also be easily carried and
   stored in formats such as XML [W3C.REC-xml-19980210] or JSON
   [I-D.jennings-senml] [RFC4627].  Using URNs in these formats is often
   preferable as they are universally recognized, self-describing, and
   therefore avoid the need for agreeing to interpret an octet string as
   a specific form of a MAC address, for instance.

   This memo defines identity URN types for situations where no such
   convenient type already exist.  For instance,
   [I-D.montemurro-gsma-imei-urn] defines International Mobile station
   Equipment Identity (IMEI) identifiers for use with 3GPP cellular
   systems.  Similarly, [I-D.atarius-dispatch-meid-urn] defines Mobile
   Equipment Identity (MEID) identifiers for use with 3GPP2 cellular
   systems.  Those URN types should be employed when such identities are
   transported; this memo does not redefine these identifiers in any

   Universally Unique IDentifier (UUID) URNs [RFC4122] are another
   alternative way for representing device identifiers, and already
   support MAC addresses as one of 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.  UUID-based identifiers are recommended
   for all general purpose uses when MAC addresses are available as
   identifiers.  The device URN defined in this memo is recommended for
   constrained environments.

   Future device identifier types can extend the device device URN type
   defined here, or define their own URNs.

   The rest of this memo 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, 1-wire device identifiers, and
   cryptographically defined identifiers.  Section 5 gives examples.
   Section 6 discusses the security considerations of the new URN type.
   Finally, Section 7 specifies the IANA registration for the new URN

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   type and sets requirements for subtype allocations within this type.

2.  Requirements language

   In this document, the key words "MAY", "MUST, "MUST NOT", "OPTIONAL",
   "RECOMMENDED", "SHOULD", and "SHOULD NOT", are to be interpreted as
   described in [RFC2119].

3.  DEV URN Definition

   Namespace ID: "dev" requested

   Registration Information: This is the first registration of this
   namespace, 2011-08-27.

   Registration version number: 1

   Registration date: 2011-08-27

   Declared registrant of the namespace: IETF and the CORE working
   group.  Should the working group cease to exist, discussion should be
   directed to the general IETF discussion forums or the IESG.

   Declaration of syntactic structure: The identifier is expressed in
   ASCII (UTF-8) characters and has a hierarchical structure as follows:

     devurn = "urn:dev:" subtype ":" hexstring componentpart
     subtype = "mac" / "ow" / "cgi"
     componentpart = [ "-" component [ componentpart ]]
     component = *1(DIGIT / ALPHA)
     hexstring = hexbyte /
                 hexbyte hexstring
     hexbyte = hexdigit hexdigit
     hexdigit = DIGIT / hexletter
     hexletter = "a" / "b" / "c" / "d" / "e" / "f" /
                 "A" / "B" / "C" / "D" / "E" / "F"

   The above Augmented Backus-Naur Form (ABNF) uses the DIGIT and ALPHA
   rules defined in [RFC5234], which are not repeated here.

   The device identity namespace includes three subtypes, and more may
   be defined in the future as specified in Section 7.

   The optional components following the hexstring are strings depicting
   individual aspects of a device.  The specific strings and their
   semantics are up to the designers of the device, but could be used to

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   refer to specific interfaces or functions within the device.

   Relevant ancillary documentation: See Section 4.

   Identifier uniqueness considerations: Device identifiers are
   generally expected to be unique, barring the accidental issue of
   multiple devices with the same identifiers.

   Identifier persistence considerations: This URN type SHOULD only be
   used for persistent identifiers, such as hardware-based identifiers
   or cryptographic identifiers based on keys intended for long-term

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

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

   Rules for Lexical Equivalence: The lexical equivalence of the DEV URN
   is defined as an exact, but not case-sensitive, string match.  While
   uppercase letters are accepted, all systems that construct or display
   DEV URNs MUST employ lower case letters.  This is necessary to ensure
   that searches, processing rules, and other potentially case sensitive
   tools have uniformly lower-case identifiers to look at.

   Conformance with URN Syntax: The string representation of the device
   identity URN and of the MEID sub namespace is fully compatible with
   the URN syntax.

   Validation Mechanism: Specific subtypes may be validated through
   mechanisms discussed in Section 4.

   Scope: DEV URN is global in scope.

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.

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   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 Ethernet 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 FFFF
   hexadecimal.  The last three octets of the Ethernet 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 FFFE is used

   Identifier assignment for all of these identifiers rests within the

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 byte family code, 48 bit
   identifier unique within a family, and 8 bit CRC code [OW].

      *) 1-Wire is a registered trademark.

   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.  Cryptographically Generated Identifiers

   DEV URNs with the "cgi" subtype represent cryptographically
   identified devices.  These identifiers are variable length but the
   hexstring MUST be at least 16 characters long (128 bits).  The
   hexstring MUST have an even number of characters.

   This memo does not define the construction of the cryptographic
   identifiers or the algorithms used in the construction, as these are
   up to the specific implementations.  It should be noted, however,
   that the use of cryptographic identifiers for anything else as tokens
   of identification will require the communicating parties to agree on
   how they are used, and what algorithms and methods are used to verify

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   an ownership claim, for instance.  These are outside the scope of
   this draft, however.  The authors observe that the use of plain
   identifiers independent of the actual cryptography that goes inside
   the identifier is possible.  For instance, Cryptographically
   Generated Addresses (CGAs) [RFC3972] can be used by parties that are
   unaware of how they were constructed, and that ownership proofs and
   other advanced functionality are made separately [RFC3971].

   Identifier assignment rests on individual devices and manufacturers;
   no coordinated identifier assignment or guaranteed uniqueness exists.
   However, the 128 bit or longer identifiers are very unlikely to
   collide, as long as their generation employs sound cryptographic
   principles and proper sources of randomness are used where necessary.

5.  Examples

   The following three examples provide examples of MAC-based, 1-Wire,
   and Cryptographic identifiers:

          urn:dev:mac:0024befffe804ff1  # The MAC address of
                                        # Jari's laptop

          urn:dev:ow:10e2073a01080063   # The 1-Wire temperature
                                        # sensor in Jari's kitchen

          urn:dev:cgi:fd4a5bf6ffb4ca6c  # The example hash output
                                        # for a CGA from RFC 3972
                                        # (before modifications to
                                        # convert it to an IP address)

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 by the user.  An implementation of the DEV URN MUST NOT
   change these properties from what they were intended.  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 memo should be construed to override what
   the relevant device specifications have already said about the

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

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7.  IANA Considerations

   Additional subtypes for DEV URNs can be defined through IETF Review
   or IESG Approval [RFC5226].

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.

   [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "Uniform Resource Names (URN) Namespace Definition
              Mechanisms", BCP 66, RFC 3406, October 2002.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

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

   [OW]       IEEE, "Overview of 1-Wire(R) Technology and Its Use",

8.2.  Informative References

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure

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              Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              July 2005.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

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

              Shelby, Z., Hartke, K., Bormann, C., and B. Frank,
              "Constrained Application Protocol (CoAP)",
              draft-ietf-core-coap-06 (work in progress), May 2011.

              Jennings, C., "Media Type for Sensor Markup Language
              (SENML)", draft-jennings-senml-05 (work in progress),
              March 2011.

              Arkko, J., Rissanen, H., Loreto, S., Turanyi, Z., and O.
              Novo, "Implementing Tiny COAP Sensors",
              draft-arkko-core-sleepy-sensors-01 (work in progress),
              July 2011.

              Arkko, J. and A. Keranen, "CoAP Security Architecture",
              draft-arkko-core-security-arch-00 (work in progress),
              July 2011.

              Montemurro, M., "A Uniform Resource Name Namespace For The
              GSM Association (GSMA) and the  International Mobile
              station Equipment Identity(IMEI)",
              draft-montemurro-gsma-imei-urn-01 (work in progress),
              February 2007.

              Atarius, R., "A Uniform Resource Name Namespace for the

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              Device Identity and the Mobile Equipment Identity (MEID)",
              draft-atarius-dispatch-meid-urn-01 (work in progress),
              August 2011.

Appendix A.  Acknowledgments

   The authors would like to thank Christer Holmberg and Ahmad Muhanna
   for interesting discussions in this problem space.  We would also
   like to note prior documents that focused on specific device
   identifiers, such as [I-D.montemurro-gsma-imei-urn] or

Authors' Addresses

   Jari Arkko
   Jorvas  02420


   Cullen Jennings
   170 West Tasman Drive
   San Jose, CA  95134

   Phone: +1 408 421-9990

   Zach Shelby
   Kidekuja 2
   Vuokatti  88600

   Phone: +358407796297

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