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rfc:rfc8064

Internet Engineering Task Force (IETF) F. Gont Request for Comments: 8064 SI6 Networks / UTN-FRH Updates: 2464, 2467, 2470, 2491, 2492, A. Cooper

       2497, 2590, 3146, 3572, 4291,                             Cisco
       4338, 4391, 5072, 5121                                D. Thaler

Category: Standards Track Microsoft ISSN: 2070-1721 W. Liu

                                                   Huawei Technologies
                                                         February 2017
        Recommendation on Stable IPv6 Interface Identifiers

Abstract

 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 in RFC 7217 in such
 cases, and recommends against embedding stable link-layer addresses
 in IPv6 IIDs.  It formally updates RFC 2464, RFC 2467, RFC 2470, RFC
 2491, RFC 2492, RFC 2497, RFC 2590, RFC 3146, RFC 3572, RFC 4291, RFC
 4338, RFC 4391, RFC 5072, and RFC 5121.  This document does not
 change any existing recommendations concerning the use of temporary
 addresses as specified in RFC 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 in Section 2 of RFC 7841.
 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/rfc8064.

Gont, et al. Standards Track [Page 1] RFC 8064 Default Interface Identifiers February 2017

Copyright Notice

 Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . .   4
 3.  Generation of IPv6 Interface Identifiers with SLAAC . . . . .   5
 4.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   5
 5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
 6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

Gont, et al. Standards Track [Page 2] RFC 8064 Default Interface Identifiers February 2017

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
 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 Interface

Gont, 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 in RFC 2119 [RFC2119].

Gont, et al. Standards Track [Page 4] RFC 8064 Default Interface Identifiers February 2017

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 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 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. 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 2017

6. References

6.1. 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 2017

Authors' 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.com

Gont, et al. Standards Track [Page 9]

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