Exceptions to the Standard Subnet Boundary in IPv6 Addressing
draft-farmer-6man-exceptions-64-09

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6man Working Group                                             D. Farmer
Internet-Draft                                        Univ. of Minnesota
Intended status: Standards Track                          August 9, 2018
Expires: February 10, 2019

     Exceptions to the Standard Subnet Boundary in IPv6 Addressing
                   draft-farmer-6man-exceptions-64-09

Abstract

   This document clarifies exceptions to the standard subnet 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 the parameters of an IPv6
   subnet.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on February 10, 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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Farmer                  Expires February 10, 2019               [Page 1]
Internet-Draft   Exceptions to the IPv6 Subnet Boundary      August 2018

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Exceptions to the Standard Subnet Boundary  . . . . . . . . .   4
     2.1.  Unicast Addresses with the First Three Bits 000 . . . . .   4
     2.2.  Manually Configured Addresses . . . . . . . . . . . . . .   5
     2.3.  DHCPv6 Assigned Addresses . . . . . . . . . . . . . . . .   5
     2.4.  IPv6 On-link Determination  . . . . . . . . . . . . . . .   6
     2.5.  IPv6 Link-type Specific Documents . . . . . . . . . . . .   6
   3.  Operational Guidance  . . . . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Change log [RFC Editor: Please remove]  . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Options for Configuring IPv6 Subnets . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   The standard subnet boundary in IPv6 addressing provides the basis
   for unicast addresses to be autonomously generated, using stateless
   address auto-configuration (SLAAC) [RFC4862], and assigned to
   interfaces on host.  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 standard
   64-bit interface identifiers (IIDs) and therefore 64-bit subnet
   prefixes, as described in the IPv6 Addressing Architecture [RFC4291]
   Section 2.5.  For additional discussion of the standard subnet
   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 assigned to interfaces on nodes as opaque 128-bit quantities
   without any knowledge of the internal structure or the subnets
   present on the link network.  These circumstances are also described
   in IPv6 Addressing Architecture [RFC4291] Section 2.5, "a node may
   consider that unicast addresses (including its own) have no internal
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