Privacy Extensions for Stateless Address Autoconfiguration in IPv6
RFC 4941

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 05

Network Working Group                                          T. Narten
Request for Comments: 4941                               IBM Corporation
Obsoletes: 3041                                                R. Draves
Category: Standards Track                             Microsoft Research
                                                             S. Krishnan
                                                       Ericsson Research
                                                          September 2007

   Privacy Extensions for Stateless Address Autoconfiguration in IPv6

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   Nodes use IPv6 stateless address autoconfiguration to generate
   addresses using a combination of locally available information and
   information advertised by routers.  Addresses are formed by combining
   network prefixes with an interface identifier.  On an interface that
   contains an embedded IEEE Identifier, the interface identifier is
   typically derived from it.  On other interface types, the interface
   identifier is generated through other means, for example, via random
   number generation.  This document describes an extension to IPv6
   stateless address autoconfiguration for interfaces whose interface
   identifier is derived from an IEEE identifier.  Use of the extension
   causes nodes to generate global scope addresses from interface
   identifiers that change over time, even in cases where the interface
   contains an embedded IEEE identifier.  Changing the interface
   identifier (and the global scope addresses generated from it) over
   time makes it more difficult for eavesdroppers and other information
   collectors to identify when different addresses used in different
   transactions actually correspond to the same node.

Narten, et al.              Standards Track                     [Page 1]
RFC 4941             Privacy Extensions to Autoconf       September 2007

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Conventions Used in This Document  . . . . . . . . . . . .  4
     1.2.  Problem Statement  . . . . . . . . . . . . . . . . . . . .  4
   2.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Extended Use of the Same Identifier  . . . . . . . . . . .  5
     2.2.  Address Usage in IPv4 Today  . . . . . . . . . . . . . . .  6
     2.3.  The Concern with IPv6 Addresses  . . . . . . . . . . . . .  7
     2.4.  Possible Approaches  . . . . . . . . . . . . . . . . . . .  8
   3.  Protocol Description . . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Assumptions  . . . . . . . . . . . . . . . . . . . . . . . 10
     3.2.  Generation of Randomized Interface Identifiers . . . . . . 10
       3.2.1.  When Stable Storage Is Present . . . . . . . . . . . . 11
       3.2.2.  In The Absence of Stable Storage . . . . . . . . . . . 12
       3.2.3.  Alternate Approaches . . . . . . . . . . . . . . . . . 12
     3.3.  Generating Temporary Addresses . . . . . . . . . . . . . . 13
     3.4.  Expiration of Temporary Addresses  . . . . . . . . . . . . 14
     3.5.  Regeneration of Randomized Interface Identifiers . . . . . 15
     3.6.  Deployment Considerations  . . . . . . . . . . . . . . . . 16
   4.  Implications of Changing Interface Identifiers . . . . . . . . 17
   5.  Defined Constants  . . . . . . . . . . . . . . . . . . . . . . 18
   6.  Future Work  . . . . . . . . . . . . . . . . . . . . . . . . . 18
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   8.  Significant Changes from RFC 3041  . . . . . . . . . . . . . . 19
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 20
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 20
     10.2. Informative References . . . . . . . . . . . . . . . . . . 20

Narten, et al.              Standards Track                     [Page 2]
RFC 4941             Privacy Extensions to Autoconf       September 2007

1.  Introduction

   Stateless address autoconfiguration [ADDRCONF] defines how an IPv6
   node generates addresses without the need for a Dynamic Host
   Configuration Protocol for IPv6 (DHCPv6) server.  Some types of
   network interfaces come with an embedded IEEE Identifier (i.e., a
   link-layer MAC address), and in those cases, stateless address
   autoconfiguration uses the IEEE identifier to generate a 64-bit
   interface identifier [ADDRARCH].  By design, the interface identifier
   is likely to be globally unique when generated in this fashion.  The