Exceptions to the 64-bit Boundary in IPv6 Addressing
draft-farmer-6man-exceptions-64-01

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6man Working Group                                             D. Farmer
Internet-Draft                                   University of Minnesota
Intended status: Standards Track                           July 24, 2018
Expires: January 25, 2019

          Exceptions to the 64-bit Boundary in IPv6 Addressing
                   draft-farmer-6man-exceptions-64-01

Abstract

   This document clarifies exceptions to the 64-bit boundary in IPv6
   addressing.  The exceptions include, unicast IPv6 addresses with the
   first three bits 000, manually configured addresses, DHCPv6 assigned
   addresses, IPv6 on-link determination, and the possibility of an
   exception specified in separate IPv6 link-type specific documents.
   Further, operational guidance is provided and Appendix A discusses
   the valid options for configuring IPv6 subnets.

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   This Internet-Draft will expire on January 25, 2019.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Internet-Draft      Exceptions to the 64-bit Boundary          July 2018

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Exceptions to the 64-bit Boundary . . . . . . . . . . . . . .   5
     2.1.  Unicast Addresses with the First Three Bits 000 . . . . .   5
     2.2.  Manually Configured Addresses . . . . . . . . . . . . . .   5
     2.3.  DHCPv6 Assigned Addresses . . . . . . . . . . . . . . . .   6
     2.4.  IPv6 On-link Determination  . . . . . . . . . . . . . . .   6
     2.5.  IPv6 Link-type Specific Documents . . . . . . . . . . . .   6
   3.  Operational Guidance  . . . . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Change log [RFC Editor: Please remove]  . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Appendix A.  Options for Configuring IPv6 Subnets . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   The 64-bit boundary in IPv6 addressing provides the basis for unicast
   addresses to be autonomously generated using stateless address
   auto-configuration (SLAAC) [RFC4862].  SLAAC allows hosts to connect
   to link networks without any pre-configuration, which is especially
   useful for general-purpose hosts and mobile devices.  In this
   circumstance, unicast addresses have an internal structure composed
   of 64-bit interface identifiers (IIDs) and therefore 64-bit subnet
   prefixes, as defined in the IPv6 Addressing Architecture
   [RFC4291bis].  For additional discussion of the 64-bit boundary in
   IPv6 addressing see RFC 7421 [RFC7421].

   However, in other circumstances, such as with manually configured
   addresses or DHCPv6 [RFC3315] assigned addresses, unicast addresses
   are considered to have no internal structure and are assigned to
   interfaces on hosts as opaque 128-bit quantities without any
   knowledge of the subnets present on the link network.  The idea that
   unicast addresses may have no internal structure is also defined in
   IPv6 Addressing Architecture [RFC4291bis], "a node may consider that
   unicast addresses (including its own) have no internal structure."

   Further, unlike IPv4 where there is a single subnet mask parameter
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