RFC 2929 (rfc2929) - Page 2 of 12

Domain Name System (DNS) IANA Considerations

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RFC 2929                DNS IANA Considerations           September 2000


1. Introduction

   The Domain Name System (DNS) provides replicated distributed secure
   hierarchical databases which hierarchically store "resource records"
   (RRs) under domain names.

   This data is structured into CLASSes and zones which can be
   independently maintained.  See [RFC 1034, 1035, 2136, 2181, 2535]
   familiarity with which is assumed.

   This document covers, 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.

   IANA currently maintains a web page of DNS parameters.  See
   .

   "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, 2535]:

                                           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.




Eastlake, et al.         Best Current Practice
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