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rfc:rfc7043

Internet Engineering Task Force (IETF) J. Abley Request for Comments: 7043 Dyn, Inc. Category: Informational October 2013 ISSN: 2070-1721

    Resource Records for EUI-48 and EUI-64 Addresses in the DNS

Abstract

 48-bit Extended Unique Identifier (EUI-48) and 64-bit Extended Unique
 Identifier (EUI-64) are address formats specified by the IEEE for use
 in various layer-2 networks, e.g., Ethernet.
 This document describes two new DNS resource record types, EUI48 and
 EUI64, for encoding Ethernet addresses in the DNS.
 This document describes potentially severe privacy implications
 resulting from indiscriminate publication of link-layer addresses in
 the DNS.  EUI-48 or EUI-64 addresses SHOULD NOT be published in the
 public DNS.  This document specifies an interoperable encoding of
 these address types for use in private DNS namespaces, where the
 privacy concerns can be constrained and mitigated.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7043.

Abley Informational [Page 1] RFC 7043 Resource Records for EUI-48, EUI-64 October 2013

Copyright Notice

 Copyright (c) 2013 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
 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 . . . . . . . . . . . . . . . . . . . . . . . . .   3
 3.  The EUI48 Resource Record . . . . . . . . . . . . . . . . . .   3
   3.1.  EUI48 RDATA Wire Format . . . . . . . . . . . . . . . . .   4
   3.2.  EUI48 RR Presentation Format  . . . . . . . . . . . . . .   4
   3.3.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   4
 4.  The EUI64 Resource Record . . . . . . . . . . . . . . . . . .   4
   4.1.  EUI64 RDATA Wire Format . . . . . . . . . . . . . . . . .   4
   4.2.  EUI64 RR Presentation Format  . . . . . . . . . . . . . .   5
   4.3.  Example . . . . . . . . . . . . . . . . . . . . . . . . .   5
 5.  Example Use Case: IP Address Tracking in DOCSIS Networks  . .   5
 6.  DNS Protocol Considerations . . . . . . . . . . . . . . . . .   6
 7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
 8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
 9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
 10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   10.1.  Normative References . . . . . . . . . . . . . . . . . .   7
   10.2.  Informative References . . . . . . . . . . . . . . . . .   8

Abley Informational [Page 2] RFC 7043 Resource Records for EUI-48, EUI-64 October 2013

1. Introduction

 The Domain Name System (DNS) is described in [RFC1034] and [RFC1035].
 This base specification defines many resource record (RR) types, and
 subsequent specifications have defined others.  Each defined RR type
 provides a means of encoding particular data in the DNS.
 48-bit Extended Unique Identifier (EUI-48) [EUI48] and 64-bit
 Extended Unique Identifier (EUI-64) [EUI64] are address formats
 specified by the IEEE for use in various layer-2 networks, e.g.,
 Ethernet.
 This document defines two new RR types, EUI48 and EUI64, for encoding
 EUI-48 and EUI-64 addresses in the DNS.
 There are potentially severe privacy implications resulting from the
 indiscriminate publication of link-layer addresses in the DNS (see
 Section 8).  This document recommends that EUI-48 or EUI-64 addresses
 SHOULD NOT be published in the public DNS.  This document specifies
 an interoperable encoding of these address types for use in private
 DNS namespaces, where the privacy implications can be constrained and
 mitigated.

2. Terminology

 This document uses capitalized keywords such as MUST and MAY to
 describe the requirements for using the registered RR types.  The
 intended meaning of those keywords in this document are the same as
 those described in [RFC2119].  Although these keywords are often used
 to specify normative requirements in IETF Standards, their use in
 this document does not imply that this document is a standard of any
 kind.

3. The EUI48 Resource Record

 The EUI48 resource record (RR) is used to store a single EUI-48
 address in the DNS.
 The Type value for the EUI48 RR is 108 (decimal).
 The EUI48 RR is class independent.
 The EUI48 RR has no special Time-to-Live (TTL) requirements.

Abley Informational [Page 3] RFC 7043 Resource Records for EUI-48, EUI-64 October 2013

3.1. EUI48 RDATA Wire Format

 The RDATA for an EUI48 RR consists of a single, 6-octet Address
 field, encoded in network (big-endian) order.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          EUI-48 Address                       |
    |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3.2. EUI48 RR Presentation Format

 The Address field MUST be represented as six two-digit hexadecimal
 numbers separated by hyphens.  The hexadecimal digits "A" through "F"
 MAY be represented in either upper or lower case.

3.3. Example

 The following EUI48 RR stores the EUI-48 unicast address
 00-00-5e-00-53-2a.
   host.example. 86400 IN EUI48 00-00-5e-00-53-2a

4. The EUI64 Resource Record

 The EUI64 RR is used to store a single EUI-64 address in the DNS.
 The Type value for the EUI64 RR is 109 (decimal).
 The EUI64 RR is class independent.
 The EUI64 RR has no special TTL requirements.

4.1. EUI64 RDATA Wire Format

 The RDATA for an EUI64 RR consists of a single, 8-octet Address
 field, encoded in network (big-endian) order.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          EUI-64 Address                       |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Abley Informational [Page 4] RFC 7043 Resource Records for EUI-48, EUI-64 October 2013

4.2. EUI64 RR Presentation Format

 The Address field MUST be represented as eight two-digit hexadecimal
 numbers separated by hyphens.  The hexadecimal digits "A" through "F"
 MAY be represented in either upper or lower case.

4.3. Example

 The following EUI64 RR stores the EUI-64 unicast address
 00-00-5e-ef-10-00-00-2a.
   host.example. 86400 IN EUI64 00-00-5e-ef-10-00-00-2a

5. Example Use Case: IP Address Tracking in DOCSIS Networks

 Canadian cable Internet subscribers are assigned IP addresses using
 DHCP, using a DHCP server operated by a cable company.  In the case
 where a cable company provides last-mile connectivity to a subscriber
 on behalf of a third-party company (reseller), the DHCP server
 assigns addresses from a pool supplied by the reseller.  The reseller
 retains knowledge of the EUI-48 address of the DOCSIS modem supplied
 to the subscriber but has no direct knowledge of the IP addresses
 assigned.  In order for the reseller to be able to map the IP address
 assigned to a subscriber to that EUI-48 address (and hence to the
 subscriber identity), the cable company can make available
 information from the DHCP server that provides (EUI-48, IP) address
 mapping.
 Cable companies in Canada are required [NTRE038D] to make this
 address mapping available using the DNS.  Zones containing the
 relevant information are published on DNS servers, access to which is
 restricted to the resellers corresponding to particular sets of
 subscribers.  Subscriber address information is not published in the
 public DNS.
 Existing DNS schemas for the representation of (EUI-48, IP) mapping
 used by Canadian cable companies are varied and inefficient; in the
 absence of an RR type for direct encoding of EUI-48 addresses,
 addresses are variously encoded into owner names or are published in
 TXT records.
 The specification in this document facilitates a more efficient,
 consistent, and reliable representation of (EUI-48, IP) mapping than
 was previously available.

Abley Informational [Page 5] RFC 7043 Resource Records for EUI-48, EUI-64 October 2013

6. DNS Protocol Considerations

 The specification of the new RR types in this document has no effect
 on the address resolution behavior of any previously existing network
 processes or protocols.  Proposals or specifications to modify or
 augment address resolution processes or protocols by making use of
 these RR types should specify how any address conflicts or use of
 multiple EUI48/EUI64 RRs are handled.

7. IANA Considerations

 IANA has assigned the RR type value 108 (decimal) for EUI48 and 109
 (decimal) for EUI64.  The corresponding entries in the "Resource
 Record (RR) TYPEs" subregistry (http://www.iana.org/assignments/
 dns-parameters/) match the following data:
          +-------+-------+-------------------+---------------+
          | Type  | Value | Meaning           | Reference     |
          +-------+-------+-------------------+---------------+
          | EUI48 | 108   | an EUI-48 address | this document |
          | EUI64 | 109   | an EUI-64 address | this document |
          +-------+-------+-------------------+---------------+

8. Security Considerations

 There are privacy concerns with the publication of link-layer
 addresses in the DNS.  EUI-48 and EUI-64 addresses with the
 Local/Global bit zero [RFC7042] (referred to in [RFC4291] as the
 universal/local bit) are intended to represent unique identifiers for
 network connected equipment, notwithstanding many observed cases of
 duplication due to manufacturing errors, unauthorized use of
 Organizationally Unique Identifiers (OUIs), and address spoofing
 through configuration of network interfaces.  Publication of EUI-48
 or EUI-64 addresses in the DNS may result in privacy issues in the
 form of unique trackable identities that in some cases may be
 permanent.
 For example, although IP addresses and DNS names for network devices
 typically change over time, EUI-48 and EUI-64 addresses configured on
 the same devices are normally far more stable (in many cases,
 effectively invariant).  Publication of EUI-48 addresses associated
 with user devices in a way that could be mapped to assigned IP
 addresses would allow the behavior of those users to be tracked by
 third parties, regardless of where and how the user's device is
 connected to the Internet.  This might well result in a loss of
 privacy for the user.

Abley Informational [Page 6] RFC 7043 Resource Records for EUI-48, EUI-64 October 2013

 The publication of EUI-48 or EUI-64 addresses associated with
 deployed equipment, using the mechanism described in this document or
 any other mechanism, has the potential to facilitate Media Access
 Control (MAC) cloning -- that is, facilitate link-layer attacks
 against deployed devices, e.g., to disrupt service or intercept data.
 These concerns can be mitigated by restricting access to DNS zones
 containing EUI48 or EUI64 RRs to specific, authorized clients and by
 provisioning them in DNS zones that exist in private namespaces only.
 This document recommends that EUI-48 or EUI-64 addresses SHOULD NOT
 be published in the public DNS.

9. Acknowledgements

 The author acknowledges the contributions of Olafur Gudmundsson, Mark
 Smith, Andrew Sullivan, Roy Arends, Michael StJohns, Donald Eastlake
 III, Randy Bush, and John Klensin.

10. References

10.1. Normative References

 [EUI48]    IEEE, "Guidelines for use of a 48-bit Extended Unique
            Identifier (EUI-48)",
            <http://standards.ieee.org/develop/regauth/tut/eui48.pdf>.
 [EUI64]    IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)",
            November 2012,
            <http://standards.ieee.org/develop/regauth/tut/eui64.pdf>.
 [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
            STD 13, RFC 1034, November 1987.
 [RFC1035]  Mockapetris, P., "Domain names - implementation and
            specification", STD 13, RFC 1035, November 1987.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC7042]  Eastlake 3rd, D. and J. Abley, "IANA Considerations and
            IETF Protocol and Documentation Usage for IEEE 802
            Parameters", BCP 141, RFC 7042, October 2013.

Abley Informational [Page 7] RFC 7043 Resource Records for EUI-48, EUI-64 October 2013

10.2. Informative References

 [NTRE038D]
            CRTC Interconnection Steering Committee (CISC) Network
            Working Group, "Implementation of IP Address Tracking in
            DOCSIS Networks (TIF18)", NTRE038D Consensus Report,
            October 2006,
            <http://www.crtc.gc.ca/public/cisc/nt/NTRE038D.doc>.
 [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
            Architecture", RFC 4291, February 2006.

Author's Address

 Joe Abley
 Dyn, Inc.
 470 Moore Street
 London, ON  N6C 2C2
 Canada
 Phone: +1 519 670 9327
 EMail: jabley@dyn.com

Abley Informational [Page 8]

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