-
INTERNET-DRAFT Andreas Gustafsson
-draft-ietf-dnsext-unknown-rrs-04.txt Nominum Inc.
- September 2002
+draft-ietf-dnsext-unknown-rrs-05.txt Nominum Inc.
+ March 2003
+
+Updates: RFC 1034, RFC 2163, RFC 2535
+
- Handling of Unknown DNS RR Types
+ Handling of Unknown DNS Resource Record Types
Status of this Memo
Abstract
- Extending the Domain Name System with new Resource Record types
+ Extending the Domain Name System with new Resource Record (RR) types
currently requires changes to name server software. This document
specifies the changes necessary to allow future DNS implementations
to handle new RR types transparently.
slave servers for the zone containing it, and in some cases also at
caching name servers and forwarders used by the client.
- Because the deployment of new server software is slow and expensive,
- the potential of the DNS in supporting new services has never been
-
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+ Because the deployment of new server software is slow and expensive,
+ the potential of the DNS in supporting new services has never been
fully realized. This memo proposes changes to name servers and to
procedures for defining new RR types aimed at simplifying the future
deployment of new RR types.
which now contains unrelated data. This would cause the compressed
name to be corrupted.
- To avoid such corruption, servers MUST NOT compress domain names
-
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+ To avoid such corruption, servers MUST NOT compress domain names
embedded in the RDATA of types that are class-specific or not well-
known. This requirement was stated in RFC1123 without defining the
term "well-known"; it is hereby specified that only the RR types
defined in RFC1035 are to be considered "well-known".
+ The specifications of a few existing RR types have explicitly allowed
+ compression contrary to this specification: RFC2163 specified that
+ compression applies to the PX RR, and RFC2535 allowed compression in
+ SIG RRs and NXT RRs records. Since this specification disallows
+ compression in these cases, it is an update to RFC2163 (section 4)
+ and RFC2535 (sections 4.1.7 and 5.2).
+
Receiving servers MUST decompress domain names in RRs of well-known
type, and SHOULD also decompress RRs of type RP, AFSDB, RT, SIG, PX,
NXT, NAPTR, and SRV (although the current specification of the SRV RR
herein rather than a traditional type-specific
encoding.
+
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An unsigned decimal integer specifying the
RDATA length in octets.
the actual RDATA field, each containing an even
number of hexadecimal digits.
-
-
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If the RDATA is of zero length, the text representation contains only
the \# token and the single zero representing the length.
This implies that embedded domain names, being included in the
overall bitwise comparison, are compared in a case-sensitive manner.
+
+
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As a result, when a new RR type contains one or more embedded domain
names, it is possible to have multiple RRs owned by the same name
that differ only in the character case of the embedded domain
records differing only in character case, and not expected to cause
any problems in practice.
-
-
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-
7. DNSSEC Canonical Form and Ordering
- DNSSEC [RFC2535] defines a canonical form and ordering for RRs. In
- the canonical form, domain names embedded in the RDATA are converted
- to lower case.
-
- To ensure backwards compatibility, this canonical form remains
- unchanged for any RR types defined in RFC2931 or earlier. That is,
- the domain names embedded in RRs of type NS, MD, MF, CNAME, SOA, MB,
- MG, MR, PTR, HINFO, MINFO, MX, HINFO, RP, AFSDB, RT, SIG, PX, NXT,
- NAPTR, KX, SRV, DNAME, and A6 are converted to lower case according
- to the DNS rules for character comparisons.
-
- For all other RR types, the canonical form is hereby changed such
- that no downcasing of embedded domain names takes place. The owner
- name is always set to lower case according to the DNS rules for
- character comparisons, regardless of the RR type.
+ DNSSEC defines a canonical form and ordering for RRs [RFC2535,
+ section 8.1]. In that canonical form, domain names embedded in the
+ RDATA are converted to lower case.
+
+ The downcasing is necessary to ensure the correctness of DNSSEC
+ signatures when case distinctions in domain names are lost due to
+ compression, but since it requires knowledge of the presence and
+ position of embedded domain names, it cannot be applied to unknown
+ types.
+
+ To ensure continued consistency of the canonical form of RR types
+ where compression is allowed, and for continued interoperability with
+ existing implementations that already implement the RFC2535 canonical
+ form and apply it to their known RR types, the canonical form remains
+ unchanged for all RR types whose whose initial publication as an RFC
+ was prior to the initial publication of this specification as an RFC
+ (RFC TBD).
+
+ As a courtesy to implementors, it is hereby noted that the complete
+ set of such previously published RR types that contain embedded
+ domain names, and whose DNSSEC canonical form therefore involves
+ downcasing according to the DNS rules for character comparisons,
+ consists of the RR types NS, MD, MF, CNAME, SOA, MB, MG, MR, PTR,
+ HINFO, MINFO, MX, HINFO, RP, AFSDB, RT, SIG, PX, NXT, NAPTR, KX, SRV,
+ DNAME, and A6.
+
+ This document specifies that for all other RR types (whether treated
+ as unknown types or treated as known types according to an RR type
+ definition RFC more recent than than RFC TBD), the canonical form is
+ such that no downcasing of embedded domain names takes place, and
+ otherwise identical to the canonical form specified in RFC2535
+ section 8.1.
+
+ Note that the owner name is always set to lower case according to the
+ DNS rules for character comparisons, regardless of the RR type.
+
+ The DNSSEC canonical RR ordering is as specified in RFC2535 section
+ 8.3, where the octet sequence is the canonical form as revised by
+ this specification.
+
+
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- The canonical ordering is as specified in RFC2535 section 8.3, where
- the octet sequence is the canonical form as revised by this
- specification.
8. Additional Section Processing
This specification is not believed to cause any new security
problems, nor to solve any existing ones.
-References
+Normative References
[RFC1034] - Domain Names - Concepts and Facilities, P. Mockapetris,
November 1987.
[RFC1035] - Domain Names - Implementation and Specifications, P.
Mockapetris, November 1987.
+ [RFC1123] - Requirements for Internet Hosts -- Application and
+ Support, R. Braden, Editor, October 1989.
+ [RFC2119] - Key words for use in RFCs to Indicate Requirement Levels,
+ S. Bradner, BCP 14, March 1997.
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+ [RFC2535] - Domain Name System Security Extensions. D. Eastlake,
+ March 1999.
+ [RFC2613] - Using the Internet DNS to Distribute MIXER Conformant
+ Global Address Mapping (MCGAM), C. Allocchio, January 1998.
- [RFC1123] - Requirements for Internet Hosts -- Application and
- Support, R. Braden, Editor, October 1989.
+ [RFC2929] - Domain Name System (DNS) IANA Considerations, D.
+ Eastlake, E. Brunner-Williams, B. Manning, September 2000.
+
+Non-normative References
[RFC1876] - A Means for Expressing Location Information in the Domain
Name System, C. Davis, P. Vixie, T. Goodwin, I. Dickinson, January
1996.
+
+
+
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[RFC2052] - A DNS RR for specifying the location of services (DNS
SRV), A. Gulbrandsen, P. Vixie, October 1996. Obsoleted by RFC2782.
- [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [RFC2136] - Dynamic Updates in the Domain Name System (DNS UPDATE).
+ [RFC2136] - Dynamic Updates in the Domain Name System (DNS UPDATE),
P. Vixie, Ed., S. Thomson, Y. Rekhter, J. Bound, April 1997.
- [RFC2535] - Domain Name System Security Extensions. D. Eastlake,
- March 1999.
-
[RFC2782] - A DNS RR for specifying the location of services (DNS
- SRV). A. Gulbrandsen, P. Vixie, L. Esibov, February 2000.
-
- [RFC2929] - Domain Name System (DNS) IANA Considerations. D.
- Eastlake, E. Brunner-Williams, B. Manning, September 2000.
+ SRV), A. Gulbrandsen, P. Vixie, L. Esibov, February 2000.
Author's Address
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
-
-
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document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
- MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
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+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
+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
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projects / thirdparty / bind9.git / commitdiff
