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rfc:rfc1886

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.

Thompson & Huitema Standards Track [Page 1] RFC 1886 IPv6 DNS Extensions December 1995

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).

Thompson & Huitema Standards Track [Page 2] RFC 1886 IPv6 DNS Extensions December 1995

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

Thompson & Huitema Standards Track [Page 3] RFC 1886 IPv6 DNS Extensions December 1995

 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.

Thompson & Huitema Standards Track [Page 4] RFC 1886 IPv6 DNS Extensions December 1995

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

Thompson & Huitema Standards Track [Page 5]

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