IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                    SI6 Networks / UTN-FRH
Updates: 2464, 2467, 2470,  2491, 2492,                        A. Cooper
         2497, 2590, 3146, 3572, 4291,                             Cisco
         4338, 4391, 4944, 5072, 5121                          D. Thaler
         (if approved)                                         Microsoft
Intended status: Standards Track                                  W. Liu
Expires: January 7, February 20, 2016                           Huawei Technologies
                                                            July 6,
                                                         August 19, 2015

          Recommendation on Stable IPv6 Interface Identifiers


   The IPv6 addressing architecture defines Modified EUI-64 format
   Interface Identifiers, and the existing IPv6 over various link-layers
   specify how such identifiers are derived from the underlying link-
   layer address (e.g., an IEEE LAN MAC address) when employing IPv6
   Stateless Address Autoconfiguration (SLAAC).  The security and
   privacy implications of embedding link-layer addresses in the
   Interface Identifier have been known and understood for some time
   now, and some popular IPv6 implementations have already deviated from
   such schemes to mitigate these issues.  This document changes the
   recommended default Interface Identifier generation scheme for SLAAC
   to that specified in RFC7217, and recommends against embedding link-
   layer addresses in IPv6 Interface Identifiers.  It formally updates
   RFC2464, RFC2467, RFC2470, RFC2491, RFC2492, RFC2497, RFC2590,
   RFC3146, RFC3572, RFC4291, RFC4338, RFC4391, RFC4944, RFC5072, and
   RFC5121, which require IPv6 Interface Identifiers to be derived from
   the underlying link-layer address.  Additionally, this document
   provides advice about the generation of Interface Identifiers with
   other address configuration mechanisms, such as Dynamic Host
   Configuration Protocol version 6 (DHCPv6) and manual configuration.

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
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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 January 7, February 20, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Generation of IPv6 Interface Identifiers with SLAAC . . . . .   4
   4.  Generation of IPv6 Interface Identifiers with DHCPv6  . . . .   4
   5.  Generation of IPv6 Interface Identifiers with Manual
       Configuration . . . . . . . . . . . . . . . . . . . . . . . .   4   5
   6.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8   9

1.  Introduction

   [RFC4862] specifies Stateless Address Autoconfiguration (SLAAC) for
   IPv6 [RFC2460], which typically results in hosts configuring one or
   more "stable" addresses composed of a network prefix advertised by a
   local router, and an Interface Identifier (IID) [RFC4291] that
   typically embeds a link-layer address (e.g., an IEEE LAN MAC

   In some network technologies and adaptation layers, the use of an IID
   based on a link-layer address may offer some advantages.  For
   example, the IP-over-IEEE802.15.4 standard in [RFC6775] allows for
   compression of IPv6 addresses when the IID is based on the underlying
   link-layer address.

   The security and privacy implications of embedding a link-layer
   address in an IPv6 IID have been known for some time now, and are
   discussed in great detail in
   [I-D.ietf-6man-ipv6-address-generation-privacy]; they include:

   o  Network activity correlation

   o  Location tracking

   o  Address scanning

   o  Device-specific vulnerability exploitation

   Some popular IPv6 implementations have already deviated from the
   traditional stable IID generation scheme to mitigate the
   aforementioned security and privacy implications [Microsoft].

   As a result of the aforementioned issues, this document recommends
   the implementation of an alternative scheme ([RFC7217]) as the
   default stable IID generation scheme for SLAAC, such that the
   aforementioned issues are mitigated.

   NOTE: [RFC4291] defines the "Modified EUI-64 format" for IIDs.
   Appendix A of [RFC4291] then describes how to transform an IEEE
   EUI-64 identifier, or an IEEE 802 48-bit MAC address from which an
   EUI-64 identifier is derived, into an IID in the Modified EUI-64

   Finally this document provides advice about the generation of
   Interface Identifiers with other address configuration mechanisms,
   such as Dynamic Host Configuration Protocol version 6 (DHCPv6) and
   manual configuration.

2.  Terminology

   Stable address:
      An address that does not vary over time within the same network
      (as defined in [I-D.ietf-6man-ipv6-address-generation-privacy]).

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  Generation of IPv6 Interface Identifiers with SLAAC

   Link layers MUST define a mechanism that provides mitigation of the
   security and privacy implications discussed in Section 1.  Nodes
   SHOULD implement and employ [RFC7217] as the default scheme for
   generating stable IPv6 addresses with SLAAC.  A link layer MAY also
   define a mechanism that is more efficient and does not address the
   security and privacy considerations discussed in Section 1.  The
   choice of whether to enable privacy or not SHOULD be configurable in
   such a case.

   By default, nodes SHOULD NOT employ IPv6 address generation schemes
   that embed the underlying link-layer address in the IID.  In
   particular, this document RECOMMENDS that nodes do not generate IIDs
   with the schemes specified in [RFC2464], [RFC2467], [RFC2470],
   [RFC2491], [RFC2492], [RFC2497], [RFC2590], [RFC3146], [RFC3572],
   [RFC4338], [RFC4391], [RFC4944], [RFC5121], and [RFC5072], and
   updates these documents with this recommendation.

   Some link-layers support locally assigned link-layer addresses
   [IEEE-802], such as [IEEE-802.3] and [IEEE-802.11], or random
   addresses [BLUETOOTH].  Where IPv6 IIDs are to be derived from link-
   layer addresses, it is RECOMMENDED that the random addresses
   supported by the link-layer are used, or that pseudo-random locally
   assigned link-layer addresses are generated, assigned and used.

   Future specifications SHOULD NOT specify IPv6 address generation
   schemes that embed the underlying link-layer address in the IID.  In
   some cases, embedding the link-layer address in the IID may reduce
   resource requirements such as energy, bandwidth and number of frames
   to carry a given IPv6 packet by facilitating header compression in
   constrained devices.  In such cases, future specifications MAY
   include IPv6 address generation schemes that embed the link-layer
   address in the IID, but MUST also specify an alternative IPv6 address
   generation scheme that provides mitigation of the security and
   privacy implications discussed in Section 1.

4.  Generation of IPv6 Interface Identifiers with DHCPv6

   By default, DHCPv6 server implementations SHOULD NOT generate
   predictable IPv6 addresses (such as IPv6 addresses where the IIDs are
   consecutive small numbers).  [I-D.ietf-dhc-stable-privacy-addresses]
   specifies one possible algorithm that could be employed to comply
   with this requirement.  Another possible algorithm would be to select
   a pseudo-random value chosen from a discrete uniform distribution,
   while avoiding the reserved IPv6 Interface Identifiers [RFC5453]

5.  Generation of IPv6 Interface Identifiers with Manual Configuration

   Network administrators should be aware of the security implications
   of predictable Interface Identifiers
   [I-D.ietf-6man-ipv6-address-generation-privacy], and avoid the use of
   predictable addresses when the aforementioned issues are of concern.

6.  Future Work

   At the time of this writing, the mechanisms specified in the
   following documents might require updates to be fully compatible with
   the recommendations in this document:

   o  RFC 6282 [RFC6282]

   o  RFC 4944 [RFC4944]

   o  RFC 6755 [RFC6775]

   Future revisions or updates of these documents should take the issues
   of privacy and security mentioned in Section 1 and explain any design
   and engineering considerations that lead to the use of IIDs based on
   a node's link-layer address.

7.  IANA Considerations

   There are no IANA registries within this document.  The RFC-Editor
   can remove this section before publication of this document as an

8.  Security Considerations

   This document recommends [RFC7217] as the default scheme for
   generating IPv6 stable addresses with SLAAC, such that the security
   and privacy issues of IIDs that embed link-layer addresses are

9.  Acknowledgements

   The authors would like to thank Erik Nordmark and Ray Hunter for
   providing a detailed review of this document.

   The authors would like to thank (in alphabetical order) Fred Baker,
   Carsten Bormann, Scott Brim, Brian Carpenter, Samita Chakrabarti, Tim
   Chown, Lorenzo Colitti, Jean-Michel Combes, Greg Daley, Esko Dijk,
   Ralph Droms, David Farmer, Brian Haberman, Ulrich Herberg, Bob
   Hinden, Philip Homburg, Jahangir Hossain, Jonathan Hui, Christian
   Huitema, Ray Hunter, Sheng Jiang, Roger Jorgensen, Dan Luedtke, Kerry
   Lynn, George Mitchel, Gabriel Montenegro, Erik Nordmark, Simon
   Perreault, Tom Petch, Alexandru Petrescu, Michael Richardson, Arturo
   Servin, Mark Smith, Tom Taylor, Ole Troan, Tina Tsou, Glen Turner,
   Randy Turner, and James Woodyatt, for providing valuable comments on
   earlier versions of this document.

10.  References

10.1.  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. 1997,

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998. 1998, <http://www.rfc-editor.org/info/rfc2460>.

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998. 1998,

   [RFC2467]  Crawford, M., "Transmission of IPv6 Packets over FDDI
              Networks", RFC 2467, DOI 10.17487/RFC2467, December 1998. 1998,

   [RFC2470]  Crawford, M., Narten, T., and S. Thomas, "Transmission of
              IPv6 Packets over Token Ring Networks", RFC 2470,
              DOI 10.17487/RFC2470, December
              1998. 1998,

   [RFC2492]  Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM
              Networks", RFC 2492, DOI 10.17487/RFC2492, January 1999. 1999,

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2003.
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February 2006.
              2006, <http://www.rfc-editor.org/info/rfc4291>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007. 2007,

   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217,
              DOI 10.17487/RFC7217, April 2014. 2014,

   [RFC2491]  Armitage, G., Schulter, P., Jork, M., and G. Harter, "IPv6
              over Non-Broadcast Multiple Access (NBMA) networks",
              RFC 2491, DOI 10.17487/RFC2491, January 1999. 1999,

   [RFC2497]  Souvatzis, I., "Transmission of IPv6 Packets over ARCnet
              Networks", RFC 2497, DOI 10.17487/RFC2497, January 1999. 1999,

   [RFC2590]  Conta, A., Malis, A., and M. Mueller, "Transmission of
              IPv6 Packets over Frame Relay Networks Specification",
              RFC 2590, DOI 10.17487/RFC2590, May 1999. 1999,

   [RFC3146]  Fujisawa, K. and A. Onoe, "Transmission of IPv6 Packets
              over IEEE 1394 Networks", RFC 3146, DOI 10.17487/RFC3146,
              October 2001. 2001, <http://www.rfc-editor.org/info/rfc3146>.

   [RFC3572]  Ogura, T., Maruyama, M., and T. Yoshida, "Internet
              Protocol Version 6 over MAPOS (Multiple Access Protocol
              Over SONET/SDH)", RFC 3572, DOI 10.17487/RFC3572, July 2003.
              2003, <http://www.rfc-editor.org/info/rfc3572>.

   [RFC4338]  DeSanti, C., Carlson, C., and R. Nixon, "Transmission of
              IPv6, IPv4, and Address Resolution Protocol (ARP) Packets
              over Fibre Channel", RFC 4338, DOI 10.17487/RFC4338,
              January 2006. 2006, <http://www.rfc-editor.org/info/rfc4338>.

   [RFC4391]  Chu, J. and V. Kashyap, "Transmission of IP over
              InfiniBand (IPoIB)", RFC 4391, DOI 10.17487/RFC4391, April 2006.
              2006, <http://www.rfc-editor.org/info/rfc4391>.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007. 2007,

   [RFC5121]  Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S.
              Madanapalli, "Transmission of IPv6 via the IPv6
              Convergence Sublayer over IEEE 802.16 Networks", RFC 5121,
              DOI 10.17487/RFC5121, February 2008. 2008,

   [RFC5072]  Varada, S., Ed., Haskins, D., and E. Allen, "IP Version 6
              over PPP", RFC 5072, DOI 10.17487/RFC5072, September 2007. 2007,

   [RFC5453]  Krishnan, S., "Reserved IPv6 Interface Identifiers",
              RFC 5453, DOI 10.17487/RFC5453, February 2009. 2009,

   [RFC6282]  Hui, J. J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011. 2011,

   [RFC6775]  Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
              Bormann, "Neighbor Discovery Optimization for IPv6 over
              Low-Power Wireless Personal Area Networks (6LoWPANs)",
              RFC 6775, DOI 10.17487/RFC6775, November 2012. 2012,

10.2.  Informative References

              IEEE, "802-2014 - IEEE Standard for Local and Metropolitan
              Area Networks: Overview and Architecture", 2014,

              IEEE, "802.3-2012 - IEEE Standard for Ethernet", 2012,

              IEEE, "IEEE Standard for Information technology --
              Telecommunications and information exchange between
              systems -- Local and metropolitan area networks --
              Specific requirements -- Part 11: Wireless LAN Medium
              Access Control (MAC) and Physical Layer (PHY)
              Specifications", 2012,

              Bluetooth SIG, "BLUETOOTH SPECIFICATION Version 4.2",
              2014, <https://www.bluetooth.org/DocMan/handlers/

              IANA, "Reserved IPv6 Interface Identifiers",

              Cooper, A., Gont, F., and D. Thaler, "Privacy
              Considerations for IPv6 Address Generation Mechanisms",
              draft-ietf-6man-ipv6-address-generation-privacy-07 (work
              in progress), June 2015.

              Gont, F. and S. LIU, "A Method for Generating Semantically
              Opaque Interface Identifiers with Dynamic Host
              Configuration Protocol for IPv6 (DHCPv6)", draft-ietf-dhc-
              stable-privacy-addresses-02 (work in progress), April

              Davies, J., "Understanding IPv6, 3rd. ed",  page 83,
              Microsoft Press, 2012, <http://it-ebooks.info/book/1022/>.

Authors' Addresses

   Fernando Gont
   SI6 Networks / UTN-FRH
   Evaristo Carriego 2644
   Haedo, Provincia de Buenos Aires  1706

   Phone: +54 11 4650 8472
   Email: fgont@si6networks.com
   URI:   http://www.si6networks.com

   Alissa Cooper
   707 Tasman Drive
   Milpitas, CA  95035

   Phone: +1-408-902-3950
   Email: alcoop@cisco.com
   URI:   https://www.cisco.com/
   Dave Thaler
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052

   Phone: +1 425 703 8835
   Email: dthaler@microsoft.com

   Will Liu
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen  518129
   P.R. China

   Email: liushucheng@huawei.com