Domain Name System (DNS) IANA Considerations
RFC 5395

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Network Working Group                                    D. Eastlake 3rd
Request for Comments: 5395                              Stellar Switches
BCP: 42                                                    November 2008
Obsoletes: 2929
Updates: 1183, 3597
Category: Best Current Practice

              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) 2008 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Abstract

   Internet Assigned Number Authority (IANA) parameter assignment
   considerations are specified for the allocation of Domain Name System
   (DNS) resource record types, CLASSes, operation codes, error codes,
   DNS protocol message header bits, and AFSDB resource record subtypes.

Eastlake                 Best Current Practice                  [Page 1]
RFC 5395                DNS IANA Considerations            November 2008

Table of Contents

   1. Introduction ....................................................2
      1.1. Terminology ................................................2
   2. DNS Query/Response Headers ......................................3
      2.1. One Spare Bit? .............................................4
      2.2. OpCode Assignment ..........................................4
      2.3. RCODE Assignment ...........................................4
   3. DNS Resource Records ............................................6
      3.1. RRTYPE IANA Considerations .................................7
           3.1.1. DNS RRTYPE Allocation Policy ........................8
           3.1.2. DNS RRTYPE Expert Guidelines ........................9
           3.1.3. Special Note on the OPT RR ..........................9
           3.1.4. The AFSDB RR Subtype Field .........................10
      3.2. RR CLASS IANA Considerations ..............................10
      3.3. Label Considerations ......................................12
           3.3.1. Label Types ........................................12
           3.3.2. Label Contents and Use .............................12
   4. Security Considerations ........................................13
   5. IANA Considerations ............................................13
   Appendix A. RRTYPE Allocation Template ............................14
   Normative References ..............................................15
   Informative References ............................................16

1.  Introduction

   The Domain Name System (DNS) provides replicated distributed secure
   hierarchical databases that store "resource records" (RRs) under
   domain names.  DNS data is structured into CLASSes and zones that can
   be independently maintained.  See [RFC1034], [RFC1035], [RFC2136],
   [RFC2181], and [RFC4033], familiarity with which is assumed.

   This document provides, either directly or by reference, the general
   IANA parameter assignment considerations that apply across DNS query
   and response headers and all RRs.  There may be additional IANA
   considerations that apply to only a particular RRTYPE or
   query/response OpCode.  See the specific RFC defining that RRTYPE or
   query/response OpCode for such considerations if they have been
   defined, except for AFSDB RR considerations [RFC1183], which are
   included herein.  This RFC obsoletes [RFC2929].

   IANA currently maintains a web page of DNS parameters available from
   http://www.iana.org.

1.1.  Terminology

   "IETF Standards Action", "IETF Review", "Specification Required", and
   "Private Use" are as defined in [RFC5226].

Eastlake                 Best Current Practice                  [Page 2]
RFC 5395                DNS IANA Considerations            November 2008

2.  DNS Query/Response Headers

   The header for DNS queries and responses contains field/bits in the
   following diagram taken from [RFC2136] and [RFC2929]:

                                              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                |