Network Working Group                                         S. Thomson
Request for Comments: 1886                                      Bellcore
Category: Standards Track                                     C. Huitema
                                                                   INRIA
                                                           December 1995

DNS Extensions to support IP version 6

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.

Abstract

   This document defines the changes that need to be made to the Domain
   Name System to support hosts running IP version 6 (IPv6).  The
   changes include a new resource record type to store an IPv6 address,
   a new domain to support lookups based on an IPv6 address, and updated
   definitions of existing query types that return Internet addresses as
   part of additional section processing.  The extensions are designed
   to be compatible with existing applications and, in particular, DNS
   implementations themselves.

1. INTRODUCTION

   Current support for the storage of Internet addresses in the Domain
   Name System (DNS)[1,2] cannot easily be extended to support IPv6
   addresses[3] since applications assume that address queries return
   32-bit IPv4 addresses only.

   To support the storage of IPv6 addresses we define the following
   extensions:

      o A new resource record type is defined to map a domain name to an
        IPv6 address.

      o A new domain is defined to support lookups based on address.

      o Existing queries that perform additional section processing to
        locate IPv4 addresses are redefined to perform additional
        section processing on both IPv4 and IPv6 addresses.

   The changes are designed to be compatible with existing software. The
   existing support for IPv4 addresses is retained. Transition issues
   related to the co-existence of both IPv4 and IPv6 addresses in DNS
   are discussed in [4].

2. NEW RESOURCE RECORD DEFINITION AND DOMAIN

   A new record type is defined to store a host's IPv6 address. A host
   that has more than one IPv6 address must have more than one such
   record.

2.1 AAAA record type

   The AAAA resource record type is a new record specific to the
   Internet class that stores a single IPv6 address.

   The value of the type is 28 (decimal).

2.2 AAAA data format

A 128 bit IPv6 address is encoded in the data portion of an AAAA
resource record in network byte order (high-order byte first).

2.3 AAAA query

   An AAAA query for a specified domain name in the Internet class
   returns all associated AAAA resource records in the answer section of
   a response.

   A type AAAA query does not perform additional section processing.

2.4 Textual format of AAAA records

   The textual representation of the data portion of the AAAA resource
   record used in a master database file is the textual representation
   of a IPv6 address as defined in [3].

2.5 IP6.INT Domain

   A special domain is defined to look up a record given an address. The
   intent of this domain is to provide a way of mapping an IPv6 address
   to a host name, although it may be used for other purposes as well.
   The domain is rooted at IP6.INT.

   An IPv6 address is represented as a name in the IP6.INT domain by a
   sequence of nibbles separated by dots with the suffix ".IP6.INT". The
   sequence of nibbles is encoded in reverse order, i.e. the low-order
   nibble is encoded first, followed by the next low-order nibble and so
   on. Each nibble is represented by a hexadecimal digit. For example,
   the inverse lookup domain name corresponding to the address

       4321:0:1:2:3:4:567:89ab

   would be

b.a.9.8.7.6.5.0.4.0.0.0.3.0.0.0.2.0.0.0.1.0.0.0.0.0.0.0.1.2.3.4.IP6.INT.

3. MODIFICATIONS TO EXISTING QUERY TYPES

   All existing query types that perform type A additional section
   processing, i.e. name server (NS), mail exchange (MX) and mailbox
   (MB) query types, must be redefined to perform both type A and type
   AAAA additional section processing. These new definitions mean that a
   name server must add any relevant IPv4 addresses and any relevant

IPv6 addresses available locally to the additional section of a
response when processing any one of the above queries.

4. SECURITY CONSIDERATIONS

Security issues are not discussed in this memo.

5. REFERENCES

   [1]  Mockapetris, P., "Domain Names - Concepts and Facilities", STD
        13, RFC 1034, USC/Information Sciences Institute, November 1987.

   [2]  Mockapetris, P., "Domain Names - Implementation and Specifica-
        tion", STD 13, RFC 1035, USC/Information Sciences Institute,
        November 1987.

   [3]  Hinden, R., and S. Deering, Editors, "IP Version 6 Addressing
        Architecture", RFC 1884, Ipsilon Networks, Xerox PARC, December
        1995.

   [4]  Gilligan, R., and E. Nordmark, "Transition Mechanisms for IPv6
        Hosts and Routers", Work in Progress.

Authors' Addresses

   Susan Thomson
   Bellcore
   MRE 2P343
   445 South Street
   Morristown, NJ 07960
   U.S.A.

   Phone: +1 201-829-4514
   EMail: set@thumper.bellcore.com

   Christian Huitema
   INRIA, Sophia-Antipolis
   2004 Route des Lucioles
   BP 109
   F-06561 Valbonne Cedex
   France

   Phone: +33 93 65 77 15
   EMail: Christian.Huitema@MIRSA.INRIA.FR