Reaction of Stateless Address Autoconfiguration (SLAAC) to Flash- Renumbering Events
draft-ietf-v6ops-slaac-renum-02

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IPv6 Operations Working Group (v6ops)                            F. Gont
Internet-Draft                                              SI6 Networks
Intended status: Informational                                   J. Zorz
Expires: November 6, 2020                                  Go6 Institute
                                                            R. Patterson
                                                                  Sky UK
                                                             May 5, 2020

   Reaction of Stateless Address Autoconfiguration (SLAAC) to Flash-
                           Renumbering Events
                    draft-ietf-v6ops-slaac-renum-02

Abstract

   In scenarios where network configuration information related to IPv6
   prefixes becomes invalid without any explicit signaling of that
   condition (such as when a CPE crashes and reboots without knowledge
   of the previously-employed prefixes), nodes on the local network will
   continue using stale prefixes for an unacceptably long period of
   time, thus resulting in connectivity problems.  This document
   documents this problem, and discusses operational workarounds that
   may help to improve network robustness.  Additionally, it highlights
   areas where further work may be needed.

Status of This Memo

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   This Internet-Draft will expire on November 6, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Gont, et al.            Expires November 6, 2020                [Page 1]
Internet-Draft       Reaction to Renumbering Events             May 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Analysis of the Problem . . . . . . . . . . . . . . . . . . .   5
     2.1.  Use of Dynamic Prefixes . . . . . . . . . . . . . . . . .   5
     2.2.  Default Timer Values in IPv6 Stateless Address
           Autoconfiguration (SLAAC) . . . . . . . . . . . . . . . .   5
     2.3.  Recovering from Stale Network Configuration Information .   6
     2.4.  Lack of Explicit Signaling about Stale Information  . . .   7
     2.5.  Interaction Between DHCPv6-PD and SLAAC . . . . . . . . .   7
   3.  Operational Mitigations . . . . . . . . . . . . . . . . . . .   7
     3.1.  Stable Prefixes . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  SLAAC Parameter Tweaking  . . . . . . . . . . . . . . . .   8
   4.  Future Work . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   IPv6 largely assumes prefix stability, with network renumbering only
   taking place in a planned manner, with old/stale prefixes being
   phased-out via reduced prefix lifetimes, and new prefixes (with
   longer lifetimes) being introduced at the same time.  However, there
   are a number of scenarios that may lead to the so-called "flash-
   renumbering" events, where the prefix employed by a network suddenly
   becomes invalid and replaced by a new prefix.  In some of these
   scenarios, the local router producing the network renumbering event
   may try to deprecate the currently-employed prefixes (by explicitly
   signaling the network about the renumbering event), whereas in other
   scenarios it may be unable to do so.