DNS AAAA Record: DNS Extensions to Support IP Version 6
The AAAA record and IP6.ARPA domain let DNS store IPv6 addresses and look them up by address.
Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, "DNS Extensions to Support IP Version 6", STD 88, RFC 3596, DOI 10.17487/RFC3596, October 2003, <https://www.rfc-editor.org/info/rfc3596>.
@misc{rfc3596,
series = {Request for Comments},
number = 3596,
howpublished = {RFC 3596},
publisher = {RFC Editor},
doi = {10.17487/RFC3596},
url = {https://www.rfc-editor.org/info/rfc3596},
author = {S. Thomson and C. Huitema and V. Ksinant and M. Souissi},
title = {{DNS Extensions to Support IP Version 6}},
pagetotal = 8,
year = 2003,
month = oct,
} RFC text
Contents
Network Working Group S. Thomson
Request for Comments: 3596 Cisco
Obsoletes: 3152, 1886 C. Huitema
Category: Standards Track Microsoft
V. Ksinant
6WIND
M. Souissi
AFNIC
October 2003
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.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document defines the changes that need to be made to the Domain
Name System (DNS) to support hosts running IP version 6 (IPv6). The
changes include a resource record type to store an IPv6 address, a
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. New resource record definition and domain. . . . . . . . . . . 2
2.1. AAAA record type . . . . . . . . . . . . . . . . . . . . 3
2.2. AAAA data format . . . . . . . . . . . . . . . . . . . . 3
2.3. AAAA query . . . . . . . . . . . . . . . . . . . . . . . 3
2.4. Textual format of AAAA records . . . . . . . . . . . . . 3
2.5. IP6.ARPA domain. . . . . . . . . . . . . . . . . . . . . 3
3. Modifications to existing query types. . . . . . . . . . . . . 4
4. Security Considerations. . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 4
6. Intellectual Property Statement. . . . . . . . . . . . . . . . 4
Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . 5
Appendix A: Changes from RFC 1886. . . . . . . . . . . . . . . . . 6
Normative References . . . . . . . . . . . . . . . . . . . . . . . 6
Informative References . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 8
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 in the DNS, this document
defines the following extensions:
o A resource record type is defined to map a domain name to an
IPv6 address.
o A 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
the DNS are discussed in [4].
The IP protocol version used for querying resource records is
independent of the protocol version of the resource records; e.g.,
IPv4 transport can be used to query IPv6 records and vice versa.
This document combines RFC 1886 [5] and changes to RFC 1886 made by
RFC 3152 [6], obsoleting both. Changes mainly consist in replacing
the IP6.INT domain by IP6.ARPA as defined in RFC 3152.
2. New resource record definition and domain
A 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 record specific to the Internet
class that stores a single IPv6 address.
The IANA assigned 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 trigger 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 an IPv6 address as defined in [3].
2.5 IP6.ARPA Domain
A special domain is defined to look up a record given an IPv6
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.ARPA.
An IPv6 address is represented as a name in the IP6.ARPA domain by a
sequence of nibbles separated by dots with the suffix ".IP6.ARPA".
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 reverse 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.
ARPA.
3. Modifications to existing query types
All existing query types that perform type A additional section
processing, i.e., name server (NS), location of services (SRV) and
mail exchange (MX) query types, must be redefined to perform both
type A and type AAAA additional section processing. These
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
Any information obtained from the DNS must be regarded as unsafe
unless techniques specified in [7] or [8] are used. The definitions
of the AAAA record type and of the IP6.ARPA domain do not change the
model for use of these techniques.
So, this specification is not believed to cause any new security
problems, nor to solve any existing ones.
5. IANA Considerations
There are no IANA assignments to be performed.
6. Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Acknowledgments
Vladimir Ksinant and Mohsen Souissi would like to thank Sebastien
Barbin (IRISA), Luc Beloeil (France Telecom R&D), Jean-Mickael Guerin
(6WIND), Vincent Levigneron (AFNIC), Alain Ritoux (6WIND), Frederic
Roudaut (IRISA) and G6 group for their help during the RFC 1886
Interop tests sessions.
Many thanks to Alain Durand and Olafur Gudmundsson for their support.
Appendix A: Changes from RFC 1886
The following changes were made from RFC 1886 "DNS Extensions to
support IP version 6":
- Replaced the "IP6.INT" domain by "IP6.ARPA".
- Mentioned SRV query types in section 3 "MODIFICATIONS TO
EXISTING QUERY TYPES"
- Added security considerations.
- Updated references :
* From RFC 1884 to RFC 3513 (IP Version 6 Addressing
Architecture).
* From "work in progress" to RFC 2893 (Transition Mechanisms for
IPv6 Hosts and Routers).
* Added reference to RFC 1886, RFC 3152, RFC 2535 and RFC 2845.
- Updated document abstract
- Added table of contents
- Added full copyright statement
- Added IANA considerations section
- Added Intellectual Property Statement
Normative References
[1] Mockapetris, P., "Domain Names - Concepts and Facilities", STD
13, RFC 1034, November 1987.
[2] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, November 1987.
[3] Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
Addressing Architecture", RFC 3513, April 2003.
Informative References
[4] Gilligan, R. and E. Nordmark, "Transition Mechanisms for IPv6
Hosts and Routers", RFC 2893, August 2000.
[5] Thomson, S. and C. Huitema, "DNS Extensions to support IP
version 6", RFC 1886, December 1995.
[6] Bush, R., "Delegation of IP6.ARPA", BCP 49, RFC 3152, August
2001.
[7] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999
[8] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington,
"Secret Key Transaction Authentication for DNS (TSIG)", RFC
2845, May 2000.
Authors' Addresses
Susan Thomson
Cisco Systems
499 Thornall Street, 8th floor
Edison, NJ 08837
Phone: +1 732-635-3086
EMail: sethomso@cisco.com
Christian Huitema
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399
EMail: huitema@microsoft.com
Vladimir Ksinant
6WIND S.A.
Immeuble Central Gare - Bat.C
1, place Charles de Gaulle
78180, Montigny-Le-Bretonneux - France
Phone: +33 1 39 30 92 36
EMail: vladimir.ksinant@6wind.com
Mohsen Souissi
AFNIC
Immeuble International
2, rue Stephenson,
78181, Saint-Quentin en Yvelines Cedex - France
Phone: +33 1 39 30 83 40
EMail: Mohsen.Souissi@nic.fr
Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
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ISO Plain Language
On this page
§1The IPv6 DNS Extensions
Applications had assumed that DNS address queries returned 32-bit IPv4 addresses, making it difficult to add IPv6 addresses to the existing approach. RFC 3596 defines three extensions: a record type that maps a name to an IPv6 address, a domain for lookups based on an IPv6 address, and changes to existing queries that add address records to responses.
The RFC is designed to work with existing software and keeps IPv4 support. The IP version used to carry a query is independent of the IP version of the records it requests.
RFC 3596 combines RFC 1886 and changes made by RFC 3152. Its main change from those documents is use of IP6.ARPA in place of IP6.INT.
DNS can use IPv4 transport to ask for IPv6 records, or IPv6 transport to ask for IPv4 records. The extensions keep the existing IPv4 support while adding IPv6 address records and lookups.
- AAAA recordStores one IPv6 address for a name.
- IP6.ARPASupports queries based on an IPv6 address.
- Additional-section processingNS, SRV and MX responses add relevant A and AAAA records.
§2.1The AAAA Record and Query
The AAAA resource record stores one IPv6 address in the Internet class. Its DNS type value is 28. The record data holds the 128-bit address in network byte order, with the high-order byte first.
A host with more than one IPv6 address has more than one AAAA record. An AAAA query returns all associated AAAA records in the answer section of the response.
An AAAA query does not trigger additional-section processing. In a master database file, the record's text form is the IPv6 address notation defined by the cited IPv6 addressing specification.
An AAAA record stores one IPv6 address for a name. If the name has several IPv6 addresses, DNS can return several AAAA records.
§2.5Reverse Lookups with IP6.ARPA
The IP6.ARPA domain lets a client look up a record using an IPv6 address. Its intended use is mapping an address to a host name, though the RFC allows other purposes.
To form a name, write each four-bit part of the address as a hexadecimal digit, separate the digits with dots and reverse their order. Append .IP6.ARPA. The example in the RFC starts with address 4321:0:1:2:3:4:567:89ab and shows the corresponding reversed sequence of digits.
The reversed order begins with the lowest-order digit of the address. Each digit is a separate DNS label.
For a reverse lookup, write the IPv6 address as hexadecimal digits in reverse order, with dots between them. Add the IP6.ARPA ending to make the DNS name.
4321:0:1:2:3:4:567:89ab
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.ARPA.§3Additional Addresses in DNS Responses
Three existing query types already perform additional-section processing for IPv4 A records: name server (NS), service location (SRV) and mail exchange (MX). RFC 3596 requires this processing to include both A and AAAA records.
When responding to one of these queries, a name server must add relevant IPv4 and IPv6 addresses available locally to the additional section. This can provide address records for names mentioned in the response.
NS, SRV and MX responses can include relevant IPv4 and IPv6 addresses in their additional section. This gives the requester address information for the names in the response.
§4Security and IANA Considerations
The RFC says DNS information should be treated as unsafe unless the DNS Security Extensions or TSIG techniques it cites are used. Defining AAAA and IP6.ARPA does not change how those techniques work.
The document is not believed to create new security problems or solve existing ones. It also says there are no IANA assignments to perform.
These DNS extensions do not change how DNS security techniques work. The RFC says DNS answers still need those techniques when they must be trusted.
§6Changes from the Earlier IPv6 DNS Rules
RFC 3596 brings together RFC 1886 and the changes made to it by RFC 3152, and obsoletes both. It replaces the IP6.INT reverse-lookup domain with IP6.ARPA.
Other listed changes include adding SRV queries to the additional-section rules, adding security and IANA considerations, and updating references and document structure.
This RFC combines two earlier documents about IPv6 in DNS. Its main protocol change is using IP6.ARPA instead of IP6.INT for reverse lookups.