Network Working Group S. Josefsson
Request for Comments: 4027 April 2005
Category: Informational
Domain Name System Media Types
Status of This Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document registers the media types application/dns and text/dns
in accordance with RFC 2048. The application/dns media type is used
to identify data on the detached Domain Name System (DNS) format
described in RFC 2540. The text/dns media type is used to identify
master files as described in RFC 1035.
Table of Contents
1. IntrodUCtion . . . . . . . . . . . . . . . . . . . . . . . . . 1
2. MIME Type Registration of application/dns . . . . . . . . . . 2
3. MIME Type Registration of text/dns . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4
A. Disclaimer and License . . . . . . . . . . . . . . . . . . . . 5
Normative References . . . . . . . . . . . . . . . . . . . . . 5
Informative References . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5
Full Copyright Statements. . . . . . . . . . . . . . . . . . . 6
1. Introduction
Domain Name System (DNS) [1] information is traditionally stored in
text files, so-called master files or zone files. The format is
described in section 5 of RFC 1035 [2].
DNS data can also be stored in a "detached" format, intended for
archiving purposes, described in RFC 2540 [4].
This document registers MIME media types for the two data formats,
with the registration procedures described in RFC 2048 [3].
2. MIME Type Registration of application/dns
To: ietf-types@iana.org
Subject: Registration of MIME media type application/dns
MIME media type name: application
MIME suBType name: dns
Required parameters: None.
Optional parameters: None.
Encoding considerations: The data format is binary, and data must be
transfered unmodified. Using encodings intended for textual parts is
not recommended.
Security considerations: This media type identifies content as being
detached DNS information, as documented in RFC 2540 [4]. This data
may be security relevant as per RFC 2538 [7] or may be secured
information as per RFC 2535 [6]. Securing the content further may be
done with standard techniques, such as OpenPGP [5] or CMS [9], but
this is outside of the scope here. Further security assessments are
not available at this point.
Interoperability considerations: The encoding of detached DNS
information is, unlike textual master files, well defined. No
further interoperability considerations are known.
Published specification: The format of data that could be tagged with
this media type is documented in RFC 2540 [4].
Applications that use this media type: DNS-related software,
including software storing and using certificates stored in DNS.
Additional information:
Magic number(s): None.
File extension(s): Unknown.
Macintosh File Type Code(s): Unknown.
Person & email address to contact for further information:
Simon Josefsson simon@josefsson.org
Intended usage: LIMITED USE
Author/change controller: simon@josefsson.org
3. MIME Type Registration of text/dns
To: ietf-types@iana.org
Subject: Registration of MIME media type text/dns
MIME media type name: text
MIME subtype name: dns
Required parameters: None.
Optional parameters: None.
Encoding considerations: The data is textual and should be transfered
in a line-oriented mode. Text literals may contain CRLF within the
text. Binary transport is possible between systems that use the same
end-of-line conventions. Master files are in general ASCII, but
non-ASCII octet values may occur and are treated as opaque values by
DNS software (compare RFC 1035, section 5). The master file format
permits encoding arbitrary octet values by using the "\DDD" encoding.
The use of "\DDD" encoding can be more reliable than transporting
non-ASCII through MIME transports, if data passes through a gateway
that re-encodes the character data.
Security considerations: This media type identifies content as being
DNS information in "master file" format, as documented in RFC 1035
[2]. The DNS data may be security relevant as per to RFC 2538 [7],
or may be secured information as per to RFC 2535 [6]. Securing the
content further may be done with standard techniques, such as OpenPGP
[5] or CMS [9], but this is outside of the scope here. Further
security assessments are not available at this point.
Interoperability considerations: There are interoperability concerns
with master files, due to the widespread use of vendor-specific
extensions. Non-ASCII comments within master files may have been
encoded in locally chosen character sets, which may be difficult to
transport interoperably. Non-ASCII data in general can become
corrupted by re-encoding gateways. To achieve interoperability, one
can use the master file format described in the specification and the
"\DDD" encoding for non-ASCII octets. Further interoperability
issues with unrecognized RR types exist, which may be handled as
discussed in section 5 of RFC 3597 [8].
Published specification: The format of data that could be tagged with
this MIME type is documented in RFC 1035 [2].
Applications that use this media type: DNS-related software,
including software storing and using certificates stored in DNS.
Additional information:
Magic number(s): None.
File extension(s): 'soa' and 'zone' are known to be used.
Macintosh file type code(s): Unknown.
Person & email address to contact for further information:
Simon Josefsson simon@josefsson.org
Intended usage: LIMITED USE
Author/change controller: simon@josefsson.org
4. Security Considerations
Security considerations are discussed in the security considerations
clauses of the MIME registrations in sections 2 and 3.
5. IANA Considerations
The IANA has registered the MIME media types application/dns and
text/dns by using the registration templates in sections 2 and 3, as
per the procedure described in RFC 2048 [3].
6. Acknowledgements
Thanks to D. Eastlake for suggesting text/dns. Thanks to Keith Moore
and Alfred Hoenes for reviewing this document. The author
acknowledges the RSA Laboratories for supporting the work that led to
this document.
A. Disclaimer and License
Regarding this entire document or any portion of it, the author makes
no guarantees and is not responsible for any damage resulting from
its use. The author grants irrevocable permission to anyone to use,
modify, and distribute it in any way that does not diminish the
rights of anyone else to use, modify, and distribute it, provided
that redistributed derivative works do not contain misleading author
or version information. Derivative works need not be licensed under
similar terms.
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] Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
Mail Extensions (MIME) Part Four: Registration Procedures", BCP
13, RFC 2048, November 1996.
[4] Eastlake 3rd, D., "Detached Domain Name System (DNS)
Information", RFC 2540, March 1999.
Informative References
[5] Callas, J., Donnerhacke, L., Finney, H., and R. Thayer, "OpenPGP
Message Format", RFC 2440, November 1998.
[6] Eastlake 3rd, D., "Domain Name System Security Extensions", RFC
2535, March 1999.
[7] Eastlake 3rd, D. and O. Gudmundsson, "Storing Certificates in
the Domain Name System (DNS)", RFC 2538, March 1999.
[8] Gustafsson, A., "Handling of Unknown DNS Resource Record (RR)
Types", RFC 3597, September 2003.
[9] Housley, R., "Cryptographic Message Syntax (CMS)", RFC 3852,
July 2004.
Author's Address
Simon Josefsson
EMail: simon@josefsson.org
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