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Domain Name System (DNS) IANA Considerations
RFC 2929

Document type: RFC - Best Current Practice (September 2000)
Obsoleted by RFC 5395
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 2929 (Best Current Practice)
Responsible AD: (None)
Send notices to: No addresses provided

Network Working Group                                   D. Eastlake, 3rd
Request for Comments: 2929                                      Motorola
BCP: 42                                              E. Brunner-Williams
Category: Best Current Practice                                   Engage
                                                              B. Manning
                                                                     ISI
                                                          September 2000

              Domain Name System (DNS) IANA Considerations

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

Copyright Notice

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

Abstract

   Internet Assigned Number Authority (IANA) parameter assignment
   considerations are given for the allocation of Domain Name System
   (DNS) classes, Resource Record (RR) types, operation codes, error
   codes, etc.

Table of Contents

   1. Introduction.................................................  2
   2. DNS Query/Response Headers...................................  2
   2.1 One Spare Bit?..............................................  3
   2.2 Opcode Assignment...........................................  3
   2.3 RCODE Assignment............................................  4
   3. DNS Resource Records.........................................  5
   3.1 RR TYPE IANA Considerations.................................  6
   3.1.1 Special Note on the OPT RR................................  7
   3.2 RR CLASS IANA Considerations................................  7
   3.3 RR NAME Considerations......................................  8
   4. Security Considerations......................................  9
   References......................................................  9
   Authors' Addresses.............................................. 11
   Full Copyright Statement........................................ 12

Eastlake, et al.         Best Current Practice                  [Page 1]
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
   <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, 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                  [Page 2]
RFC 2929                DNS IANA Considerations           September 2000

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

   The AA, TC, RD, RA, AD, and CD bits are each theoretically meaningful

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