Clarifications on On-link and Subnet IPv6 Prefixes
draft-jinmei-6man-prefix-clarify-00

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6man Working Group                                             T. Jinmei
Internet-Draft                                                  Infoblox
Intended status: Informational                            March 13, 2017
Expires: September 14, 2017

           Clarifications on On-link and Subnet IPv6 Prefixes
                  draft-jinmei-6man-prefix-clarify-00

Abstract

   The IPv6 Neighbor Discovery and Stateless Address Autoconfiguration
   protocols intentionally separate the handling of prefixes for their
   purposes: these prefixes can be different for the same link even if
   it may be uncommon in practice; validation for these purposes is
   expected to be performed separately and independently.  Despite the
   revised text of the latest versions of these protocol specifications,
   it appears that the idea of this separation can still be easily
   misunderstood.  This document clarifies the idea even more explicitly
   in order to set the common understanding of the intent of the current
   specifications.

Status of This Memo

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   This Internet-Draft will expire on September 14, 2017.

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Jinmei                 Expires September 14, 2017               [Page 1]
Internet-Draft      On-link and Subnet IPv6 Prefixes          March 2017

   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language and Terminology . . . . . . . . . . . .   3
   3.  Clarifications  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Implementation Status . . . . . . . . . . . . . . . . . . . .   7
   5.  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   [RFC4861] defines the Prefix Information option (PIO) of the Neighbor
   Discovery Router Advertisement (RA) message.  It is used by receiving
   hosts for on-link determination, that is, determining which prefixes
   are to be considered on-link in the link through which the RA is
   delivered.  [RFC4862] also uses the PIO for the purpose of stateless
   address autoconfiguration (SLAAC).  While a single PIO is often used
   for both purposes, the corresponding specifications intend to handle
   them separately and independently.  In particular, the prefix in a
   PIO is not expected to be considered to be invalid for on-link
   determination simply because the prefix fails to validate in SLAAC,
   or vice versa.

   The idea of separating these two purposes had often been
   misunderstood in prior specifications of [RFC4861] and [RFC4862], so
   these successor RFCs tried to clarify the intent with additional
   text.  According to a recent discussion at the 6man working group in
   the context of advancing [RFC4291], however, it turned out that it
   may still not be uncommon that the separation is misunderstood.
   There are even reportedly implementations that invalidate a prefix
   for on-link determination when it is invalid for SLAAC.  Although
   this misunderstanding would normally not cause troubles in practical
   deployments, it can be a source of operational surprise or
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