Domain Name System (DNS) IANA Considerations
RFC 2929
| Document | Type |
RFC - Best Current Practice
(September 2000; No errata)
Obsoleted by RFC 5395
|
|
|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Replaces | draft-eastlake-dnsext-2929bis | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 2929 (Best Current Practice) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
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
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
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