IPv6 maintenance Working Group (6man)                            F. Gont
Internet-Draft                                    SI6 Networks / UTN-FRH
Updates: 2464, 2467, 2470,  2491, 2492,                        A. Cooper
         2497, 2590, 3146, 3315, 3572,                             Cisco 4291,                             Cisco
         4338, 4391, 5072, 5121 (if                            D. Thaler
         approved)                                             Microsoft
Intended status: Standards Track                                  W. Liu
Expires: February 19, 21, 2017                           Huawei Technologies
                                                         August 18, 20, 2016

          Recommendation on Stable IPv6 Interface Identifiers


   This document changes the recommended default IID generation scheme
   for cases where SLAAC is used to generate a stable IPv6 address.  It
   recommends using the mechanism specified in RFC7217 in such cases,
   and recommends against embedding stable link-layer addresses in IPv6
   Interface Identifiers.  It formally updates RFC2464, RFC2467,
   RFC2470, RFC2491, RFC2492, RFC2497, RFC2590, RFC3146, RFC3572,
   RFC4291, RFC4338, RFC4391, RFC5072, and RFC5121.  This document does
   not change any existing recommendations concerning the use of
   temporary addresses as specified in RFC 4941.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 19, 21, 2017.

Copyright Notice

   Copyright (c) 2016 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
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   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Generation of IPv6 Interface Identifiers with SLAAC . . . . .   4
   4.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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 stable 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 stable link-
   layer address in an IPv6 IID have been known for some time now, and
   are discussed in great detail in [RFC7721].  They include:

   o  Network activity correlation

   o  Location tracking

   o  Address scanning

   o  Device-specific vulnerability exploitation
   More generally, the reuse of identifiers that have their own
   semantics or properties across different contexts or scopes can be
   detrimental for security and privacy
   [I-D.gont-predictable-numeric-ids].  In the case of traditional
   stable IPv6 IIDs, some of the security and privacy implications are
   dependent on the properties of the underlying link-layer addresses
   (e.g., whether the link-layer address is ephemeral or randomly
   generated), while other implications (e.g., reduction of the entropy
   of the IID) depend on the algorithm for generating the IID itself.
   In standardized recommendations for stable IPv6 IID generation meant
   to achieve particular security and privacy properties, it is
   therefore necessary to recommend against embedding stable link-layer
   addresses in IPv6 IIDs.

   Furthermore, 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 changes the
   recommended default IID generation scheme for generating stable IPv6
   addresses with SLAAC to that specified in [RFC7217], and recommends
   against embedding stable link-layer addresses in IPv6 Interface
   Identifiers, such that the aforementioned issues are mitigated.  That
   is, this document simply replaces the default algorithm that is
   recommended to be employed when generating stable IPv6 IIDs.

   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

   In a variety of scenarios, addresses that remain stable for the
   lifetime of a host's connection to a single subnet, are viewed as
   desirable.  For example, stable addresses may be viewed as beneficial
   for network management, event logging, enforcement of access control,
   provision of quality of service, or for server or routing interfaces.
   Similarly, stable addresses (as opposed to temporary addresses
   [RFC4941]) allow for long-lived TCP connections, and are also usually
   desirable when performing server-like functions (i.e., receiving
   incoming connections).

   The recommendations in this document apply only in cases where
   implementations otherwise would have configured a stable IPv6 IID
   containing a link layer address.  For example, this document does not
   change any existing recommendations concerning the use of temporary
   addresses as specified in [RFC4941], nor do the recommendations apply
   to cases where SLAAC is employed to generate non-stable IPv6
   addresses (e.g. by embedding a link-layer address that is
   periodically randomized), nor does it introduce any new requirements
   regarding when stable addresses are to be configured.  Thus, the
   recommendations in this document simply improve the security and
   privacy properties of stable addresses.

2.  Terminology

   Stable address:
      An address that does not vary over time within the same network
      (as defined in [RFC7721]).

   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

   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 for stable IPv6 address generation that is more
   efficient and does not address the security and privacy
   considerations discussed in Section 1.  The choice of whether to
   enable the security- and privacy-preserving mechanism or not SHOULD
   be configurable in such a case.

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

4.  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  "Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based
      Networks" [RFC6282]

   o  "Transmission of IPv6 Packets over IEEE 802.15.4 Networks"

   o  "Neighbor Discovery Optimization for IPv6 over Low-Power Wireless
      Personal Area Networks (6LoWPANs)"[RFC6775]

   o  "Transmission of IPv6 Packets over ITU-T G.9959 Networks"[RFC7428]

   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 stable IIDs
   based on a node's link-layer address.

5.  IANA Considerations

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

6.  Security Considerations

   This recommends against the (default) use of predictable Interface
   Identifiers in IPv6 addresses.  It recommends [RFC7217] as the
   default scheme for generating IPv6 stable addresses with SLAAC, such
   that the security and privacy issues of IIDs that embed stable link-
   layer addresses are mitigated.

7.  Acknowledgements

   The authors would like to thank (in alphabetical order) Bob Hinden,
   Ray Hunter and Erik Nordmark, for providing a detailed review of this

   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, Philip
   Homburg, Jahangir Hossain, Jonathan Hui, Christian Huitema, Ray
   Hunter, Erik Kline, 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, James Woodyatt, and Juan Carlos Zuniga, for providing
   valuable comments on earlier versions of this document.

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,

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 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,

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

   [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,

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

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

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

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

   [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, <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, <http://www.rfc-editor.org/info/rfc4391>.

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

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,

   [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,

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

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

   [RFC6282]  Hui, 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,

   [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,

   [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,

   [RFC7428]  Brandt, A. and J. Buron, "Transmission of IPv6 Packets
              over ITU-T G.9959 Networks", RFC 7428,
              DOI 10.17487/RFC7428, February 2015,

8.2.  Informative References

              Gont, F. and I. Arce, "Security and Privacy Implications
              of Numeric Identifiers Employed in Network Protocols",
              draft-gont-predictable-numeric-ids-00 (work in progress),
              February 2016.

              IANA, "Reserved IPv6 Interface Identifiers",

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

   [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, <http://www.rfc-editor.org/info/rfc3572>.

   [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,

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