rfc2929.txt

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RFC 2929                DNS IANA Considerations           September 2000


     32768 - 65279
   0x8000 - 0xFEFF - Specification Required as defined in [RFC 2434].

     65280 - 65535
   0xFF00 - 0xFFFF - Private Use.

3.1.1 Special Note on the OPT RR

   The OPT (OPTion) RR, number 41, is specified in [RFC 2671].  Its
   primary purpose is to extend the effective field size of various DNS
   fields including RCODE, label type, flag bits, and RDATA size.  In
   particular, for resolvers and servers that recognize it, it extends
   the RCODE field from 4 to 12 bits.

3.2 RR CLASS IANA Considerations

   DNS CLASSes have been little used but constitute another dimension of
   the DNS distributed database.  In particular, there is no necessary
   relationship between the name space or root servers for one CLASS and
   those for another CLASS.  The same name can have completely different
   meanings in different CLASSes although the label types are the same
   and the null label is usable only as root in every CLASS.  However,
   as global networking and DNS have evolved, the IN, or Internet, CLASS
   has dominated DNS use.

   There are two subcategories of DNS CLASSes: normal data containing
   classes and QCLASSes that are only meaningful in queries or updates.

   The current CLASS assignments and considerations for future
   assignments are as follows:

     Decimal
   Hexadecimal

     0
   0x0000 - assignment requires an IETF Standards Action.

     1
   0x0001 - Internet (IN).

     2
   0x0002 - available for assignment by IETF Consensus as a data CLASS.

     3
   0x0003 - Chaos (CH) [Moon 1981].

     4
   0x0004 - Hesiod (HS) [Dyer 1987].



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     5 - 127
   0x0005 - 0x007F - available for assignment by IETF Consensus as data
          CLASSes only.

     128 - 253
   0x0080 - 0x00FD - available for assignment by IETF Consensus as
          QCLASSes only.

     254
   0x00FE - QCLASS None [RFC 2136].

     255
   0x00FF - QCLASS Any [RFC 1035].

     256 - 32767
   0x0100 - 0x7FFF - assigned by IETF Consensus.

     32768 - 65280
   0x8000 - 0xFEFF - assigned based on Specification Required as defined
          in [RFC 2434].

     65280 - 65534
   0xFF00 - 0xFFFE - Private Use.

     65535
   0xFFFF - can only be assigned by an IETF Standards Action.

3.3 RR NAME Considerations

   DNS NAMEs are sequences of labels [RFC 1035].  The last label in each
   NAME is "ROOT" which is the zero length label.  By definition, the
   null or ROOT label can not be used for any other NAME purpose.

   At the present time, there are two categories of label types, data
   labels and compression labels.  Compression labels are pointers to
   data labels elsewhere within an RR or DNS message and are intended to
   shorten the wire encoding of NAMEs.  The two existing data label
   types are sometimes referred to as Text and Binary.  Text labels can,
   in fact, include any octet value including zero octets but most
   current uses involve only [US-ASCII].  For retrieval, Text labels are
   defined to treat ASCII upper and lower case letter codes as matching.
   Binary labels are bit sequences [RFC 2673].

   IANA considerations for label types are given in [RFC 2671].







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   NAMEs are local to a CLASS.  The Hesiod [Dyer 1987] and Chaos [Moon
   1981] CLASSes are essentially for local use.  The IN or Internet
   CLASS is thus the only DNS CLASS in global use on the Internet at
   this time.

   A somewhat dated description of name allocation in the IN Class is
   given in [RFC 1591].  Some information on reserved top level domain
   names is in Best Current Practice 32 [RFC 2606].

4. Security Considerations

   This document addresses IANA considerations in the allocation of
   general DNS parameters, not security.  See [RFC 2535] for secure DNS
   considerations.

References

   [Dyer 1987] Dyer, S., and F. Hsu, "Hesiod", Project Athena Technical
               Plan - Name Service, April 1987,

   [Moon 1981] D. Moon, "Chaosnet", A.I. Memo 628, Massachusetts
               Institute of Technology Artificial Intelligence
               Laboratory, June 1981.

   [RFC 1034]  Mockapetris, P., "Domain Names - Concepts and
               Facilities", STD 13, RFC 1034, November 1987.

   [RFC 1035]  Mockapetris, P., "Domain Names - Implementation and
               Specifications", STD 13, RFC 1035, November 1987.

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

   [RFC 1996]  Vixie, P., "A Mechanism for Prompt Notification of Zone
               Changes (DNS NOTIFY)", RFC 1996, August 1996.

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

   [RFC 2181]  Elz, R. and R. Bush, "Clarifications to the DNS
               Specification", RFC 2181, July 1997.

   [RFC 2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
               IANA Considerations Section in RFCs", BCP 26, RFC 2434,
               October 1998.





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RFC 2929                DNS IANA Considerations           September 2000


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

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

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

   [RFC 2672]  Crawford, M., "Non-Terminal DNS Name Redirection", RFC
               2672, August 1999.

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

   [RFC 2845]  Vixie, P., Gudmundsson, O., Eastlake, D. and B.
               Wellington, "Secret Key Transaction Authentication for
               DNS (TSIG)", RFC 2845, May 2000.

   [RFC 2930]  Eastlake, D., "Secret Key Establishment for DNS (TKEY
               RR)", RFC 2930, September 2000.

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


























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Authors' Addresses

   Donald E. Eastlake 3rd
   Motorola
   140 Forest Avenue
   Hudson, MA 01749 USA

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


   Eric Brunner-Williams
   Engage
   100 Brickstone Square, 2nd Floor
   Andover, MA 01810

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


   Bill Manning
   USC/ISI
   4676 Admiralty Way, #1001
   Marina del Rey, CA 90292 USA

   Phone: [phone]
   EMail: [e-mail]




















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RFC 2929                DNS IANA Considerations           September 2000


Full Copyright Statement

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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