Reaction of Stateless Address Autoconfiguration (SLAAC) to Renumbering Events
draft-gont-6man-slaac-renum-00

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Last updated 2019-01-31
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IPv6 Maintenance (6man) Working Group                            F. Gont
Internet-Draft                                    SI6 Networks / UTN-FRH
Updates: 4861 (if approved)                                      J. Zorz
Intended status: Standards Track                        January 31, 2019
Expires: August 4, 2019

 Reaction of Stateless Address Autoconfiguration (SLAAC) to Renumbering
                                 Events
                     draft-gont-6man-slaac-renum-00

Abstract

   A very common IPv6 deployment scenario is that in which a CPE employs
   DHCPv6 Prefix Delegation to obtain an IPv6 prefix, and at least one
   prefix from within the leased prefix is advertised on a local network
   via SLAAC.  In scenarios where e.g. the CPE crashes and reboots,
   nodes on the local network continue using outdated prefixes which
   result in connectivity problems.  This document analyzes this problem
   scenario, and proposes workarounds.

Status of This Memo

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   This Internet-Draft will expire on August 4, 2019.

Copyright Notice

   Copyright (c) 2019 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
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   carefully, as they describe your rights and restrictions with respect

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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Possible workarounds  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Improvement to SLAAC  . . . . . . . . . . . . . . . . . .   3
     3.2.  Improved CPE behavior . . . . . . . . . . . . . . . . . .   5
     3.3.  Stable prefixes . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Flowchart for Host Processing of RAs . . . . . . . .   8
   Appendix B.  Sample Timeline for Host Processing of RAs . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Probably the most common deployment scenario for IPv6 in home
   networks is that in which a CPE router employs DHCPv6 Prefix
   Delegation (DHCPv6-PD) [RFC8415] to request a prefix from the ISP,
   and a prefix belonging to the leased prefix is advertised on the LAN-
   side of the CPE via Stateless Address Autoconfiguration (SLAAC)
   [RFC4862].

   In scenarios such as that in which the CPE router crashes and
   reboots, the CPE may be leased (via DHCPv6-PD) a different prefix
   than the one previously leased and will therefore advertise such new
   prefix on the LAN side via SLAAC.  Hosts will normally configure an
   address for the new prefix, but will normally retain and actively
   employ the previously-configured addresses, since their associated
   Preferred Lifetime and Valid Lifetime allow them to do so.  The
   default values, as specified in [RFC4861] are:

   o  Valid Lifetime (AdvValidLifetime): 2592000 seconds (30 days)

   o  Preferred Lifetime (AdvPreferredLifetime): 604800 seconds (7 days)

   Lacking any explicit signaling to "obsolete" the previously-
   configured addresses (for the now invalid/outdated prefix), hosts may
   continue employing the previously-configured addresses which will
   tipically result in packets being blackholed -- whether because of

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