DNS Extensions to Support IPv6 Address Aggregation and Renumbering
RFC 2874

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Network Working Group                                        M. Crawford
Request for Comments: 2874                                      Fermilab
Category: Standards Track                                     C. Huitema
                                                   Microsoft Corporation
                                                               July 2000

   DNS Extensions to Support IPv6 Address Aggregation and Renumbering

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This document defines changes to the Domain Name System to support
   renumberable and aggregatable IPv6 addressing.  The changes include a
   new resource record type to store an IPv6 address in a manner which
   expedites network renumbering and updated definitions of existing
   query types that return Internet addresses as part of additional
   section processing.

   For lookups keyed on IPv6 addresses (often called reverse lookups),
   this document defines a new zone structure which allows a zone to be
   used without modification for parallel copies of an address space (as
   for a multihomed provider or site) and across network renumbering
   events.

Crawford, et al.            Standards Track                     [Page 1]
RFC 2874                        IPv6 DNS                       July 2000

Table of Contents

   1.  Introduction ...............................................  2
   2.  Overview ...................................................  3
       2.1.  Name-to-Address Lookup ...............................  4
       2.2.  Underlying Mechanisms for Reverse Lookups ............  4
           2.2.1.  Delegation on Arbitrary Boundaries .............  4
           2.2.2.  Reusable Zones .................................  5
   3.  Specifications .............................................  5
       3.1.  The A6 Record Type ...................................  5
           3.1.1.  Format .........................................  6
           3.1.2.  Processing .....................................  6
           3.1.3.  Textual Representation .........................  7
           3.1.4.  Name Resolution Procedure ......................  7
       3.2.  Zone Structure for Reverse Lookups ...................  7
   4.  Modifications to Existing Query Types ......................  8
   5.  Usage Illustrations ........................................  8
       5.1.  A6 Record Chains .....................................  9
           5.1.1.  Authoritative Data .............................  9
           5.1.2.  Glue ........................................... 10
           5.1.3.  Variations ..................................... 12
       5.2.  Reverse Mapping Zones ................................ 13
           5.2.1.  The TLA level .................................. 13
           5.2.2.  The ISP level .................................. 13
           5.2.3.  The Site Level ................................. 13
       5.3.  Lookups .............................................. 14
       5.4.  Operational Note ..................................... 15
   6.  Transition from RFC 1886 and Deployment Notes .............. 15
       6.1.  Transition from AAAA and Coexistence with A Records .. 16
       6.2.  Transition from Nibble Labels to Binary Labels ....... 17
   7.  Security Considerations .................................... 17
   8.  IANA Considerations ........................................ 17
   9.  Acknowledgments ............................................ 18
   10.  References ................................................ 18
   11.  Authors' Addresses ........................................ 19
   12.  Full Copyright Statement .................................. 20

1.  Introduction

   Maintenance of address information in the DNS is one of several
   obstacles which have prevented site and provider renumbering from
   being feasible in IP version 4.  Arguments about the importance of
   network renumbering for the preservation of a stable routing system
   and for other purposes may be read in [RENUM1, RENUM2, RENUM3].  To
   support the storage of IPv6 addresses without impeding renumbering we
   define the following extensions.

Crawford, et al.            Standards Track                     [Page 2]
RFC 2874                        IPv6 DNS                       July 2000

   o  A new resource record type, "A6", is defined to map a domain name
      to an IPv6 address, with a provision for indirection for leading
      "prefix" bits.

   o  Existing queries that perform additional section processing to