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Internet Engineering Task Force (IETF)                           F. GontRequest for Comments: 8064                        SI6 Networks / UTN-FRHUpdates:2464,2467,2470,2491,2492,                         A. Cooper2497,2590,3146,3572,4291,                             Cisco         4338, 4391, 5072, 5121                                D. ThalerCategory: Standards Track                                      MicrosoftISSN: 2070-1721                                                   W. Liu                                                     Huawei Technologies                                                           February 2017Recommendation on Stable IPv6 Interface IdentifiersAbstract   This document changes the recommended default Interface Identifier   (IID) generation scheme for cases where Stateless Address   Autoconfiguration (SLAAC) is used to generate a stable IPv6 address.   It recommends using the mechanism specified inRFC 7217 in such   cases, and recommends against embedding stable link-layer addresses   in IPv6 IIDs.  It formally updatesRFC 2464,RFC 2467,RFC 2470,RFC2491,RFC 2492,RFC 2497,RFC 2590,RFC 3146,RFC 3572,RFC 4291,RFC4338,RFC 4391,RFC 5072, andRFC 5121.  This document does not   change any existing recommendations concerning the use of temporary   addresses as specified inRFC 4941.Status of This Memo   This is an Internet Standards Track document.   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).  Further information on   Internet Standards is available inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc8064.Gont, et al.                 Standards Track                    [Page 1]

RFC 8064              Default Interface Identifiers        February 2017Copyright Notice   Copyright (c) 2017 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .32.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .43.  Generation of IPv6 Interface Identifiers with SLAAC . . . . .54.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .55.  Security Considerations . . . . . . . . . . . . . . . . . . .56.  References  . . . . . . . . . . . . . . . . . . . . . . . . .6   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .8   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .9Gont, et al.                 Standards Track                    [Page 2]

RFC 8064              Default Interface Identifiers        February 20171.  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   address).   In some network technologies and adaptation layers, the use of an IID   based on a link-layer address may offer some advantages.  For   example, [RFC6282] allows for the compression of IPv6 datagrams over   IEEE 802.15.4-based networks [RFC4944] 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 [NUM-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 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 InterfaceGont, et al.                 Standards Track                    [Page 3]

RFC 8064              Default Interface Identifiers        February 2017   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      format.   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 router 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] and the recommendations do not   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); in addition, this document does not   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",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inRFC 2119 [RFC2119].Gont, et al.                 Standards Track                    [Page 4]

RFC 8064              Default Interface Identifiers        February 20173.  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 inSection 1.  The choice of whether or not   to enable the security- and privacy-preserving mechanism 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], [RFC5072], and [RFC5121].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"      [RFC4944]   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 consider the   issues of privacy and security mentioned inSection 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.  Security Considerations   This document 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.Gont, et al.                 Standards Track                    [Page 5]

RFC 8064              Default Interface Identifiers        February 20176.  References6.1.  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,               <http://www.rfc-editor.org/info/rfc2119>.   [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,               <http://www.rfc-editor.org/info/rfc2464>.   [RFC2467]   Crawford, M., "Transmission of IPv6 Packets over FDDI               Networks",RFC 2467, DOI 10.17487/RFC2467, December 1998,               <http://www.rfc-editor.org/info/rfc2467>.   [RFC2470]   Crawford, M., Narten, T., and S. Thomas, "Transmission of               IPv6 Packets over Token Ring Networks",RFC 2470,               DOI 10.17487/RFC2470, December 1998,               <http://www.rfc-editor.org/info/rfc2470>.   [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,               <http://www.rfc-editor.org/info/rfc2491>.   [RFC2492]   Armitage, G., Schulter, P., and M. Jork, "IPv6 over ATM               Networks",RFC 2492, DOI 10.17487/RFC2492, January 1999,               <http://www.rfc-editor.org/info/rfc2492>.   [RFC2497]   Souvatzis, I., "Transmission of IPv6 Packets over ARCnet               Networks",RFC 2497, DOI 10.17487/RFC2497, January 1999,               <http://www.rfc-editor.org/info/rfc2497>.   [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,               <http://www.rfc-editor.org/info/rfc2590>.   [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>.Gont, et al.                 Standards Track                    [Page 6]

RFC 8064              Default Interface Identifiers        February 2017   [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,               <http://www.rfc-editor.org/info/rfc4862>.   [RFC4941]   Narten, T., Draves, R., and S. Krishnan, "Privacy               Extensions for Stateless Address Autoconfiguration in               IPv6",RFC 4941, DOI 10.17487/RFC4941, September 2007,               <http://www.rfc-editor.org/info/rfc4941>.   [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, <http://www.rfc-editor.org/info/rfc4944>.   [RFC5072]   Varada, S., Ed., Haskins, D., and E. Allen, "IP Version 6               over PPP",RFC 5072, DOI 10.17487/RFC5072, September               2007, <http://www.rfc-editor.org/info/rfc5072>.   [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,               <http://www.rfc-editor.org/info/rfc5121>.   [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,               <http://www.rfc-editor.org/info/rfc6282>.   [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,               <http://www.rfc-editor.org/info/rfc6775>.Gont, et al.                 Standards Track                    [Page 7]

RFC 8064              Default Interface Identifiers        February 2017   [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,               <http://www.rfc-editor.org/info/rfc7217>.   [RFC7428]   Brandt, A. and J. Buron, "Transmission of IPv6 Packets               over ITU-T G.9959 Networks",RFC 7428,               DOI 10.17487/RFC7428, February 2015,               <http://www.rfc-editor.org/info/rfc7428>.6.2.  Informative References   [Microsoft] Davies, J., "Understanding IPv6, 3rd. ed",               page 83, Microsoft Press, 2012,               <http://it-ebooks.info/book/1022/>.   [NUM-IDS]   Gont, F. and I. Arce, "Security and Privacy Implications               of Numeric Identifiers Employed in Network Protocols",               Work in Progress, February 2016.   [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,               <http://www.rfc-editor.org/info/rfc7721>.Acknowledgements   The authors would like to thank (in alphabetical order) Bob Hinden,   Ray Hunter, and Erik Nordmark, 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, 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 draft versions of this document.Gont, et al.                 Standards Track                    [Page 8]

RFC 8064              Default Interface Identifiers        February 2017Authors' Addresses   Fernando Gont   SI6 Networks / UTN-FRH   Evaristo Carriego 2644   Haedo, Provincia de Buenos Aires  1706   Argentina   Phone: +54 11 4650 8472   Email: fgont@si6networks.com   URI:https://www.si6networks.com   Alissa Cooper   Cisco   707 Tasman Drive   Milpitas, CA  95035   United States of America   Phone: +1-408-902-3950   Email: alcoop@cisco.com   URI:https://www.cisco.com/   Dave Thaler   Microsoft   Microsoft Corporation   One Microsoft Way   Redmond, WA  98052   Phone: +1 425 703 8835   Email: dthaler@microsoft.com   Will (Shucheng) Liu   Huawei Technologies   Bantian, Longgang District   Shenzhen  518129   China   Email: liushucheng@huawei.comGont, et al.                 Standards Track                    [Page 9]