Special Use Domain Name 'ipv4only.arpa'
draft-cheshire-sudn-ipv4only-dot-arpa-06

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Last updated 2016-11-14
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Network Working Group                                        S. Cheshire
Internet-Draft                                               D. Schinazi
Updates: 7050 (if approved)                                   Apple Inc.
Intended status: Standards Track                       November 15, 2016
Expires: May 19, 2017

                Special Use Domain Name 'ipv4only.arpa'
                draft-cheshire-sudn-ipv4only-dot-arpa-06

Abstract

   The specification for how a client discovers its network's NAT64
   prefix [RFC7050] defines the special name 'ipv4only.arpa' for this
   purpose, but declares it to be a non-special name in that
   specification's Domain Name Reservation Considerations section.

   Consequently, despite the well articulated special purpose of the
   name, as of November 2016 'ipv4only.arpa' still does not appear as
   one of the names with special properties that are recorded in the
   Special-Use Domain Names registry.

   This document formally declares the actual special properties of the
   name, and adds similar declarations for the corresponding reverse
   mapping names.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on May 19, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Cheshire & Schinazi       Expires May 19, 2017                  [Page 1]
Internet-Draft         Special Name ipv4only.arpa          November 2016

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1.  Introduction

   The specification for how a client discovers its network's NAT64
   prefix [RFC7050] defines the special name 'ipv4only.arpa' for this
   purpose, but declares it to be a non-special name in that
   specification's Domain Name Reservation Considerations section.

   Consequently, despite the well articulated special purpose of the
   name, as of November 2016 'ipv4only.arpa' still does not appear as
   one of the names with special properties that are recorded in the
   Special-Use Domain Names registry [SUDN].

   This document formally declares the actual special properties of the
   name.  This document also adds similar declarations for the
   corresponding reverse mapping names.

Cheshire & Schinazi       Expires May 19, 2017                  [Page 2]
Internet-Draft         Special Name ipv4only.arpa          November 2016

2.  Specialness of 'ipv4only.arpa'

   The hostname 'ipv4only.arpa' is peculiar in that it was never
   intended to be treated like a normal hostname.

   A typical client never looks up the IPv4 address records for
   'ipv4only.arpa', because it is already known, by specification
   [RFC7050], to have exactly two IPv4 address records, 192.0.0.170 and
   192.0.0.171.  No client ever has to look the name in order to learn
   those two addresses.

   In contrast, clients often look up the IPv6 AAAA address records for
   'ipv4only.arpa', which is contrary to general DNS expectations, given
   that it is already known, by specification [RFC7050], that no such
   IPv6 AAAA address records exist.  And yet, clients expect to receive,
   and do in fact receive, positive answers for these IPv6 AAAA address
   records that are known to not exist.

   This is clearly not a typical DNS name.  In normal operation, clients
   never query for the two records that do in fact exist; instead they
   query for records that are known to not exist, and then get positive
   answers to those abnormal queries.  Clients are using DNS to perform
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