Recommendation on Stable IPv6 Interface Identifiers
RFC 8064

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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