draft-ietf-dnsext-2929bis-01.txt

bind 源码 最新实现 linux/unix/windows平台

INTERNET-DRAFT                                    Donald E. Eastlake 3rd
Obsoletes RFC 2929, Updates RFC 1183               Motorola Laboratories
Expires: February 2006                                       August 2005



              Domain Name System (DNS) IANA Considerations
              ------ ---- ------ ----- ---- --------------
                   <draft-ietf-dnsext-2929bis-01.txt>



Status of This Document

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Distribution of this draft is unlimited.  It is intended to become
   the new BCP 42 obsoleting RFC 2929.  Comments should be sent to the
   DNS Working Group mailing list <[e-mail]>.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   The list of current Internet-Drafts can be accessed at
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Abstract

   Internet Assigned Number Authority (IANA) parameter assignment
   considerations are given for the allocation of Domain Name System
   (DNS) classes, RR types, operation codes, error codes, RR header
   bits, and AFSDB subtypes.








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Table of Contents

      Status of This Document....................................1
      Abstract...................................................1

      Table of Contents..........................................2

      1. Introduction............................................3
      2. DNS Query/Response Headers..............................3
      2.1 One Spare Bit?.........................................4
      2.2 Opcode Assignment......................................4
      2.3 RCODE Assignment.......................................5
      3. DNS Resource Records....................................6
      3.1 RR TYPE IANA Considerations............................7
      3.1.1 DNS TYPE Allocation Policy...........................8
      3.1.2 Special Note on the OPT RR...........................9
      3.1.3 The AFSDB RR Subtype Field...........................9
      3.2 RR CLASS IANA Considerations...........................9
      3.3 RR NAME Considerations................................11
      4. Security Considerations................................11

      Appendix: Changes from RFC 2929...........................12

      Copyright and Disclaimer..................................13
      Normative References......................................13
      Informative References....................................14

      Authors Addresses.........................................16
      Expiration and File Name..................................16























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1. Introduction

   The Domain Name System (DNS) provides replicated distributed secure
   hierarchical databases which hierarchically store "resource records"
   (RRs) under domain names.  DNS data is structured into CLASSes and
   zones which can be independently maintained.  See [RFC 1034, 1035,
   2136, 2181, 4033] familiarity with which is assumed.

   This document provides, either directly or by reference, general IANA
   parameter assignment considerations applying across DNS query and
   response headers and all RRs.  There may be additional IANA
   considerations that apply to only a particular RR type or
   query/response opcode.  See the specific RFC defining that RR type or
   query/response opcode for such considerations if they have been
   defined, except for AFSDB RR considerations [RFC 1183] which are
   included herein. This RFC obsoletes [RFC 2929].

   IANA currently maintains a web page of DNS parameters.  See
   <http://www.iana.org/numbers.htm>.

   "IETF Standards Action", "IETF Consensus", "Specification Required",
   and "Private Use" are as defined in [RFC 2434].



2. DNS Query/Response Headers

   The header for DNS queries and responses contains field/bits in the
   following diagram taken from [RFC 2136, 2929]:

                                              1  1  1  1  1  1
                0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
               +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
               |                      ID                       |
               +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
               |QR|   Opcode  |AA|TC|RD|RA| Z|AD|CD|   RCODE   |
               +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
               |                QDCOUNT/ZOCOUNT                |
               +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
               |                ANCOUNT/PRCOUNT                |
               +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
               |                NSCOUNT/UPCOUNT                |
               +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
               |                    ARCOUNT                    |
               +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

   The ID field identifies the query and is echoed in the response so
   they can be matched.

   The QR bit indicates whether the header is for a query or a response.


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   The AA, TC, RD, RA, AD, and CD bits are each theoretically meaningful
   only in queries or only in responses, depending on the bit.  However,
   many DNS implementations copy the query header as the initial value
   of the response header without clearing bits.  Thus any attempt to
   use a "query" bit with a different meaning in a response or to define
   a query meaning for a "response" bit is dangerous given existing
   implementation.  Such meanings may only be assigned by an IETF
   Standards Action.

   The unsigned fields query count (QDCOUNT), answer count (ANCOUNT),
   authority count (NSCOUNT), and additional information count (ARCOUNT)
   express the number of records in each section for all opcodes except
   Update.  These fields have the same structure and data type for
   Update but are instead the counts for the zone (ZOCOUNT),
   prerequisite (PRCOUNT), update (UPCOUNT), and additional information
   (ARCOUNT) sections.



2.1 One Spare Bit?

   There have been ancient DNS implementations for which the Z bit being
   on in a query meant that only a response from the primary server for
   a zone is acceptable.  It is believed that current DNS
   implementations ignore this bit.

   Assigning a meaning to the Z bit requires an IETF Standards Action.



2.2 Opcode Assignment

   Currently DNS OpCodes are assigned as follows:

          OpCode Name                      Reference

           0     Query                     [RFC 1035]
           1     IQuery  (Inverse Query, Obsolete) [RFC 3425]
           2     Status                    [RFC 1035]
           3     available for assignment
           4     Notify                    [RFC 1996]
           5     Update                    [RFC 2136]
          6-15   available for assignment

   New OpCode assignments require an IETF Standards Action as modified
   by [RFC 4020].






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2.3 RCODE Assignment

   It would appear from the DNS header above that only four bits of
   RCODE, or response/error code are available.  However, RCODEs can
   appear not only at the top level of a DNS response but also inside
   OPT RRs [RFC 2671], TSIG RRs [RFC 2845], and TKEY RRs [RFC 2930].
   The OPT RR provides an eight bit extension resulting in a 12 bit
   RCODE field and the TSIG and TKEY RRs have a 16 bit RCODE field.

   Error codes appearing in the DNS header and in these three RR types
   all refer to the same error code space with the single exception of
   error code 16 which has a different meaning in the OPT RR from its
   meaning in other contexts.  See table below.

        RCODE   Name    Description                        Reference
        Decimal
          Hexadecimal
         0    NoError   No Error                           [RFC 1035]
         1    FormErr   Format Error                       [RFC 1035]
         2    ServFail  Server Failure                     [RFC 1035]
         3    NXDomain  Non-Existent Domain                [RFC 1035]
         4    NotImp    Not Implemented                    [RFC 1035]
         5    Refused   Query Refused                      [RFC 1035]
         6    YXDomain  Name Exists when it should not     [RFC 2136]
         7    YXRRSet   RR Set Exists when it should not   [RFC 2136]
         8    NXRRSet   RR Set that should exist does not  [RFC 2136]
         9    NotAuth   Server Not Authoritative for zone  [RFC 2136]
        10    NotZone   Name not contained in zone         [RFC 2136]
        11 - 15         Available for assignment
        16    BADVERS   Bad OPT Version                    [RFC 2671]
        16    BADSIG    TSIG Signature Failure             [RFC 2845]
        17    BADKEY    Key not recognized                 [RFC 2845]
        18    BADTIME   Signature out of time window       [RFC 2845]
        19    BADMODE   Bad TKEY Mode                      [RPC 2930]
        20    BADNAME   Duplicate key name                 [RPF 2930]
        21    BADALG    Algorithm not supported            [RPF 2930]

        22 - 3,840
          0x0016 - 0x0F00   Available for assignment

        3,841 - 4,095
          0x0F01 - 0x0FFF   Private Use

        4,096 - 65,534
          0x1000 - 0xFFFE   Available for assignment

        65,535
          0xFFFF            Reserved, can only be allocated by an IETF
                            Standards Action.



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   Since it is important that RCODEs be understood for interoperability,
   assignment of new RCODE listed above as "available for assignment"
   requires an IETF Consensus.



3. DNS Resource Records

   All RRs have the same top level format shown in the figure below
   taken from [RFC 1035]:

                                       1  1  1  1  1  1
         0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                                               |
       /                                               /
       /                      NAME                     /
       |                                               |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                      TYPE                     |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                     CLASS                     |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                      TTL                      |
       |                                               |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |                   RDLENGTH                    |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
       /                     RDATA                     /
       /                                               /
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

   NAME is an owner name, i.e., the name of the node to which this
   resource record pertains.  NAMEs are specific to a CLASS as described
   in section 3.2.  NAMEs consist of an ordered sequence of one or more
   labels each of which has a label type [RFC 1035, 2671].

   TYPE is a two octet unsigned integer containing one of the RR TYPE
   codes.  See section 3.1.

   CLASS is a two octet unsigned integer containing one of the RR CLASS
   codes.  See section 3.2.

   TTL is a four octet (32 bit) bit unsigned integer that specifies the
   number of seconds that the resource record may be cached before the
   source of the information should again be consulted.  Zero is
   interpreted to mean that the RR can only be used for the transaction
   in progress.

   RDLENGTH is an unsigned 16 bit integer that specifies the length in


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   octets of the RDATA field.

   RDATA is a variable length string of octets that constitutes the
   resource. The format of this information varies according to the TYPE
   and in some cases the CLASS of the resource record.



3.1 RR TYPE IANA Considerations

   There are three subcategories of RR TYPE numbers: data TYPEs, QTYPEs,
   and MetaTYPEs.

   Data TYPEs are the primary means of storing data.  QTYPES can only be
   used in queries.  Meta-TYPEs designate transient data associated with
   an particular DNS message and in some cases can also be used in
   queries.  Thus far, data TYPEs have been assigned from 1 upwards plus
   the block from 100 through 103 while Q and Meta Types have been
   assigned from 255 downwards except for the OPT Meta-RR which is
   assigned TYPE 41.  There have been DNS implementations which made
   caching decisions based on the top bit of the bottom byte of the RR
   TYPE.

   There are currently three Meta-TYPEs assigned: OPT [RFC 2671], TSIG
   [RFC 2845], and TKEY [RFC 2930].

   There are currently five QTYPEs assigned: * (all), MAILA, MAILB,
   AXFR, and IXFR.

   Considerations for the allocation of new RR TYPEs are as follows:

     Decimal
   Hexadecimal

     0
   0x0000 - TYPE zero is used as a special indicator for the SIG RR [RFC
          2535] and in other circumstances and must never be allocated
          for ordinary use.

     1 - 127
   0x0001 - 0x007F - remaining TYPEs in this range are assigned for data
          TYPEs by the DNS TYPE Allocation Policy as specified in
          section 3.1.1.

     128 - 255
   0x0080 - 0x00FF - remaining TYPEs in this rage are assigned for Q and
          Meta TYPEs by the DNS TYPE Allocation Policy as specified in
          section 3.1.1.




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     256 - 32,767
   0x0100 - 0x7FFF - assigned for data, Q, or Meta TYPE use by the DNS
          TYPE Allocation Policy as specified in section 3.1.1.

     32,768 - 65,279
   0x8000 - 0xFEFF - Specification Required as defined in [RFC 2434].

     65,280 - 65534
   0xFF00 - 0xFFFE - Private Use.

     65,535
   0xFFFF - Reserved, can only be assigned by an IETF Standards Action.



3.1.1 DNS TYPE Allocation Policy

   Parameter values specified above as assigned based on DNS TYPE
   Allocation Policy. That is, Expert Review with the additional
   requirement that the review be based on a complete template as
   specified below which has been posted for three weeks to the
   [e-mail] mailing list.

   Partial or draft templates may be posted with the intend of
   soliciting feedback.


                 DNS RR TYPE PARAMETER ALLOCATION TEMPLATE

        Date:

        Name and email of originator:

        Pointer to internet-draft or other document giving a detailed
        description of the protocol use of the new RR Type:

        What need is the new RR TYPE intended to fix?

        What existing RR TYPE(s) come closest to filling that need and why are
        they unsatisfactory?

        Does the proposed RR TYPR require special handling within the DNS
        different from an Unknown RR TYPE?

        Comments:







D. Eastlake 3rd                                                 [Page 8]