draft-ietf-dnsext-insensitive-04.txt

bind 9.3结合mysql数据库

   "name compression".



4.2 DNS Input Case Preservation

   Originally, DNS input came from an ASCII Master File as defined in
   [STD 13] or a zone transfer.  DNS Dynamic update and incremental zone
   transfers [RFC 1995] have been added as a source of DNS data [RFC
   2136, 3007]. When a node in the DNS name tree is created by any of
   such inputs, no case conversion is done. Thus the case of ASCII
   labels is preserved if they are for nodes being created. However,
   when a name label is input for a node that already exist in DNS data
   being held, the situation is more complex. Implementations may retain
   the case first input for such a label or allow new input to override
   the old case or even maintain separate copies preserving the input
   case.

   For example, if data with owner name "foo.bar.example" is input and
   then later data with owner name "xyz.BAR.example" is input, the name
   of the label on the "bar.example" node, i.e. "bar", might or might
   not be changed to "BAR" or the actual input case could be preserved.
   Thus later retrieval of data stored under "xyz.bar.example" in this
   case can easily return data with "xyz.BAR.example".  The same


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   considerations apply when inputting multiple data records with owner
   names differing only in case. For example, if an "A" record is stored
   as the first resourced record under owner name "xyz.BAR.example" and
   then a second "A" record is stored under "XYZ.BAR.example", the
   second MAY be stored with the first (lower case initial label) name
   or the second MAY override the first so that only an upper case
   initial label is retained or both capitalizations MAY be kept.

   Note that the order of insertion into a server database of the DNS
   name tree nodes that appear in a Master File is not defined so that
   the results of inconsistent capitalization in a Master File are
   unpredictable output capitalization.



5. Internationalized Domain Names

   A scheme has been adopted for "internationalized domain names" and
   "internationalized labels" as described in [RFC 3490, 3454, 3491, and
   3492]. It makes most of [UNICODE] available through a separate
   application level transformation from internationalized domain name
   to DNS domain name and from DNS domain name to internationalized
   domain name. Any case insensitivity that internationalized domain
   names and labels have varies depending on the script and is handled
   entirely as part of the transformation described in [RFC 3454] and
   [RFC 3491] which should be seen for further details.  This is not a
   part of the DNS as standardized in STD 13.



6. Security Considerations

   The equivalence of certain DNS label types with case differences, as
   clarified in this document, can lead to security problems. For
   example, a user could be confused by believing two domain names
   differing only in case were actually different names.

   Furthermore, a domain name may be used in contexts other than the
   DNS.  It could be used as a case sensitive index into some data base
   system. Or it could be interpreted as binary data by some integrity
   or authentication code system. These problems can usually be handled
   by using a standardized or "canonical" form of the DNS ASCII type
   labels, that is, always mapping the ASCII letter value octets in
   ASCII labels to some specific pre-chosen case, either upper case or
   lower case. An example of a canonical form for domain names (and also
   a canonical ordering for them) appears in Section 8 of [RFC 2535].
   See also [RFC 3597].

   Finally, a non-DNS name may be stored into DNS with the false
   expectation that case will always be preserved. For example, although


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   this would be quite rare, on a system with case sensitive email
   address local parts, an attempt to store two "RP" records that
   differed only in case would probably produce unexpected results that
   might have security implications. That is because the entire email
   address, including the possibly case sensitive local or left hand
   part, is encoded into a DNS name in a readable fashion where the case
   of some letters might be changed on output as described above.













































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Copyright and Disclaimer

   Copyright (C) The Internet Society 2004.  This document is subject to
   the rights, licenses and restrictions contained in BCP 78, and except
   as set forth therein, the authors retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM 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.



Normative References

   [ASCII] - ANSI, "USA Standard Code for Information Interchange",
   X3.4, American National Standards Institute: New York, 1968.

   [RFC 1034, 1035] - See [STD 13].

   [RFC 1995] - M. Ohta, "Incremental Zone Transfer in DNS", August
   1996.

   [RFC 2119] - S. Bradner, "Key words for use in RFCs to Indicate
   Requirement Levels", March 1997.

   [RFC 2136] - P. Vixie, Ed., S. Thomson, Y. Rekhter, J. Bound,
   "Dynamic Updates in the Domain Name System (DNS UPDATE)", April 1997.

   [RFC 2535] - D. Eastlake, "Domain Name System Security Extensions",
   March 1999.

   [RFC 3007] - B. Wellington, "Secure Domain Name System (DNS) Dynamic
   Update", November 2000.

   [RFC 3597] - Andreas Gustafsson, "Handling of Unknown DNS RR Types",
   draft-ietf-dnsext-unknown-rrs-05.txt, March 2003.

   [STD 13]
       - P. Mockapetris, "Domain names - concepts and facilities", RFC
   1034, November 1987.
       - P. Mockapetris, "Domain names - implementation and
   specification", RFC 1035, November 1987.






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Informative References

   [RFC 1591] - J. Postel, "Domain Name System Structure and
   Delegation", March 1994.

   [RFC 2606] - D. Eastlake, A. Panitz, "Reserved Top Level DNS Names",
   June 1999.

   [RFC 2929] - D. Eastlake, E. Brunner-Williams, B. Manning, "Domain
   Name System (DNS) IANA Considerations", September 2000.

   [RFC 2671] - P. Vixie, "Extension mechanisms for DNS (EDNS0)", August
   1999.

   [RFC 2673] - M. Crawford, "Binary Labels in the Domain Name System",
   August 1999.

   [RFC 3092] - D. Eastlake 3rd, C. Manros, E. Raymond, "Etymology of
   Foo", 1 April 2001.

   [RFC 3454] - P. Hoffman, M. Blanchet, "Preparation of
   Internationalized String ("stringprep")", December 2002.

   [RFC 3490] - P. Faltstrom, P. Hoffman, A. Costello,
   "Internationalizing Domain Names in Applications (IDNA)", March 2003.

   [RFC 3491] - P. Hoffman, M. Blanchet, "Nameprep: A Stringprep Profile
   for Internationalized Domain Names (IDN)", March 2003.

   [RFC 3492] - A. Costello, "Punycode: A Bootstring encoding of Unicode
   for Internationalized Domain Names in Applications (IDNA)", March
   2003.

   [UNICODE] - The Unicode Consortium, "The Unicode Standard",
   <http://www.unicode.org/unicode/standard/standard.html>.



-02 to -03 Changes

   The following changes were made between draft version -02 and -03:

   1. Add internationalized domain name section and references.

   2. Change to indicate that later input of a label for an existing DNS
   name tree node may or may not be normalized to the earlier input or
   override it or both may be preserved.

   3. Numerous minor wording changes.



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-03 to -04 Changes

   The following changes were made between draft version -03 and -04:

   1. Change to conform to the new IPR, Copyright, etc., notice
   requirements.

   2. Change in some section headers for clarity.

   3. Drop section on wildcards.

   4. Add emphasis on loss of case preservation due to name compression.

   5. Add references to RFCs 1995 and 3092.



Author's Address

   Donald E. Eastlake 3rd
   Motorola Laboratories
   155 Beaver Street
   Milford, MA 01757 USA

   Telephone:   [phone] (w)
                [phone] (h)
   EMail:       [e-mail]



Expiration and File Name

   This draft expires December 2004.

   Its file name is draft-ietf-dnsext-insensitive-04.txt.

















D. Eastlake 3rd                                                [Page 11]