DNS AAAA Record: DNS Extensions to Support IP Version 6
The AAAA record and IP6.ARPA domain that let DNS store and look up IPv6 addresses.
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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Acknowledgement
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Internet Society.
AI ELI5
On this page
§1Why DNS Needed Extending
The way DNS stores Internet addresses could not easily be extended to hold IPv6 addresses, because applications assume that address queries return 32-bit IPv4 addresses only. RFC 3596 defines three extensions: a resource record type that maps a name to an IPv6 address, a domain for lookups based on address, and a redefinition of existing queries that fill in the additional section.
The changes are designed to be compatible with existing software, and IPv4 support is kept. The IP version used to send a query is independent of the version of the records asked for, so IPv4 transport can be used to query IPv6 records and the other way round.
The old phone book only knew short numbers. Instead of throwing it away, the memo adds a new kind of entry next to the old ones.
- AAAA recordMaps a domain name to an IPv6 address.
- IP6.ARPA domainSupports lookups based on an IPv6 address.
- Additional sectionNS, SRV and MX queries now include both IPv4 and IPv6 addresses.
§2.1The AAAA Record Type
The AAAA resource record type is specific to the Internet class and stores a single IPv6 address. IANA assigned it the type value 28 (decimal). The 128-bit address is placed in the data portion in network byte order, high-order byte first.
A host that has more than one IPv6 address MUST have more than one AAAA record. In a master database file, the data is written as the textual form of an IPv6 address defined in RFC 3513.
An AAAA record is one line in the phone book with a name and one long number. A person with three numbers gets three lines.
§2.3AAAA Queries
An AAAA query for a domain name in the Internet class returns all the AAAA resource records for that name in the answer section of the response. A type AAAA query does not trigger additional section processing.
Ask for a name's long numbers and you get every long number listed for it. The answer does not come with extra pages of other information.
§2.5The IP6.ARPA Reverse Domain
A special domain, rooted at IP6.ARPA, is defined to look up a record given an IPv6 address. Its intent is to map an address to a host name, though it may be used for other purposes as well.
An address becomes a name in this domain as a sequence of nibbles (four-bit values) separated by dots, ending with the suffix .IP6.ARPA. The nibbles are in reverse order, with the low-order nibble first, and each one is written as a hexadecimal digit. For the address 4321:0:1:2:3:4:567:89ab the reverse lookup name is the 32 nibbles shown in the figure below, followed by IP6.ARPA.
To find a name from a number, you write the number backwards, one digit at a time with dots between, then add a special ending. It is like reading a street address from the house number outwards.
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.§3Changes to Existing Query Types
Queries that already add type A records to the additional section must now add AAAA records too. The RFC names three: name server (NS), location of services (SRV) and mail exchange (MX).
A name server therefore MUST add any relevant IPv4 addresses and any relevant IPv6 addresses it has locally to the additional section when it answers one of these queries.
When the phone book tells you which post office or mail server to use, it now also slips in that place's new long numbers, not just the short ones.
§4Security Considerations
Any information obtained from DNS must be regarded as unsafe unless the techniques of RFC 2535 (DNS Security Extensions) or RFC 2845 (TSIG) are used. The AAAA record and the IP6.ARPA domain do not change how those techniques are used.
The RFC says it is not believed to cause any new security problems, nor to solve any existing ones. It also states that no IANA assignments are needed.
An answer from the phone book can be wrong unless it is signed. The new entries do not make that better or worse.
§7Changes from RFC 1886
RFC 3596 combines RFC 1886 and the changes made to it by RFC 3152, and obsoletes both. The main change is replacing the IP6.INT domain with IP6.ARPA.
Other changes: SRV is mentioned among the query types in Section 3, security considerations and IANA considerations sections were added, the references were updated, and the abstract and table of contents were added or updated.
This is a tidied-up version of an older memo. The biggest change is a new ending for the backwards lookup names.