Domain Name System (DNS) Parameters

Last Updated
2019-08-01
Available Formats

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Registries included below

DNS CLASSes

Expert(s)
Unassigned
Reference
[RFC6895]
Note
As noted in [RFC6762], Multicast DNS can only carry DNS records with classes in the range 0-32767. 
Classes in the range 32768 to 65535 are incompatible with Multicast DNS.
Available Formats

CSV
Decimal Hex Registration Procedures Note
0 0x0000 Standards Action
1-127 0x0000-0x007F IETF Review data CLASSes only
128-253 0x0080-0x00FD IETF Review QCLASSes and meta-CLASSes only
256-32767 0x0100-0x7FFF IETF Review
32768-57343 0x8000-0xDFFF Specification Required data CLASSes only
57344-65279 0xE000-0xFEFF Specification Required QCLASSes and meta-CLASSes only
65280-65534 0xFF00-0xFFFE Private Use
65535 0xFFFF Standards Action
Decimal Hexadecimal Name Reference
0 0x0000 Reserved [RFC6895]
1 0x0001 Internet (IN) [RFC1035]
2 0x0002 Unassigned
3 0x0003 Chaos (CH) [D. Moon, "Chaosnet", A.I. Memo 628, Massachusetts Institute of Technology Artificial Intelligence Laboratory, June 1981.]
4 0x0004 Hesiod (HS) [Dyer, S., and F. Hsu, "Hesiod", Project Athena Technical Plan - Name Service, April 1987.]
5-253 0x0005-0x00FD Unassigned
254 0x00FE QCLASS NONE [RFC2136]
255 0x00FF QCLASS * (ANY) [RFC1035]
256-65279 0x0100-0xFEFF Unassigned
65280-65534 0xFF00-0xFFFE Reserved for Private Use [RFC6895]
65535 0xFFFF Reserved [RFC6895]

Resource Record (RR) TYPEs

Expert(s)
Roy Arends, Frederico AC Neves, Olafur Gudmundsson, Ray Bellis
Reference
[RFC6895][RFC1035]
Available Formats

CSV
Decimal Hex Registration Procedures Note
0 0x0000 RRTYPE zero is used as a special indicator for the SIG RR [RFC2931], [RFC4034] and in other circumstances and must never be allocated for ordinary use.
1-127 0x0000-0x007F Expert Review (see mailing list information in [RFC6895]) or Standards Action data TYPEs
128-255 0x0080-0x00FF Expert Review (see mailing list information in [RFC6895]) or Standards Action Q TYPEs, Meta TYPEs
256-61439 0x0100-0xEFFF Expert Review (see mailing list information in [RFC6895]) or Standards Action data RRTYPEs
61440-65279 0xF000-0xFEFF Reserved for future use (IETF Review required to define use)
65280-65534 0xFF00-0xFFFE Private Use
65535 0xFFFF Reserved (Standards Action)
TYPE Value Meaning Reference Template Registration Date
A 1 a host address [RFC1035]
NS 2 an authoritative name server [RFC1035]
MD 3 a mail destination (OBSOLETE - use MX) [RFC1035]
MF 4 a mail forwarder (OBSOLETE - use MX) [RFC1035]
CNAME 5 the canonical name for an alias [RFC1035]
SOA 6 marks the start of a zone of authority [RFC1035]
MB 7 a mailbox domain name (EXPERIMENTAL) [RFC1035]
MG 8 a mail group member (EXPERIMENTAL) [RFC1035]
MR 9 a mail rename domain name (EXPERIMENTAL) [RFC1035]
NULL 10 a null RR (EXPERIMENTAL) [RFC1035]
WKS 11 a well known service description [RFC1035]
PTR 12 a domain name pointer [RFC1035]
HINFO 13 host information [RFC1035]
MINFO 14 mailbox or mail list information [RFC1035]
MX 15 mail exchange [RFC1035]
TXT 16 text strings [RFC1035]
RP 17 for Responsible Person [RFC1183]
AFSDB 18 for AFS Data Base location [RFC1183][RFC5864]
X25 19 for X.25 PSDN address [RFC1183]
ISDN 20 for ISDN address [RFC1183]
RT 21 for Route Through [RFC1183]
NSAP 22 for NSAP address, NSAP style A record [RFC1706]
NSAP-PTR 23 for domain name pointer, NSAP style [RFC1348][RFC1637][RFC1706]
SIG 24 for security signature [RFC4034][RFC3755][RFC2535][RFC2536][RFC2537][RFC2931][RFC3110][RFC3008]
KEY 25 for security key [RFC4034][RFC3755][RFC2535][RFC2536][RFC2537][RFC2539][RFC3008][RFC3110]
PX 26 X.400 mail mapping information [RFC2163]
GPOS 27 Geographical Position [RFC1712]
AAAA 28 IP6 Address [RFC3596]
LOC 29 Location Information [RFC1876]
NXT 30 Next Domain (OBSOLETE) [RFC3755][RFC2535]
EID 31 Endpoint Identifier [Michael_Patton][http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt] 1995-06
NIMLOC 32 Nimrod Locator [1][Michael_Patton][http://ana-3.lcs.mit.edu/~jnc/nimrod/dns.txt] 1995-06
SRV 33 Server Selection [1][RFC2782]
ATMA 34 ATM Address [ ATM Forum Technical Committee, "ATM Name System, V2.0", Doc ID: AF-DANS-0152.000, July 2000. Available from and held in escrow by IANA.]
NAPTR 35 Naming Authority Pointer [RFC2915][RFC2168][RFC3403]
KX 36 Key Exchanger [RFC2230]
CERT 37 CERT [RFC4398]
A6 38 A6 (OBSOLETE - use AAAA) [RFC3226][RFC2874][RFC6563]
DNAME 39 DNAME [RFC6672]
SINK 40 SINK [Donald_E_Eastlake][http://tools.ietf.org/html/draft-eastlake-kitchen-sink] 1997-11
OPT 41 OPT [RFC6891][RFC3225]
APL 42 APL [RFC3123]
DS 43 Delegation Signer [RFC4034][RFC3658]
SSHFP 44 SSH Key Fingerprint [RFC4255]
IPSECKEY 45 IPSECKEY [RFC4025]
RRSIG 46 RRSIG [RFC4034][RFC3755]
NSEC 47 NSEC [RFC4034][RFC3755]
DNSKEY 48 DNSKEY [RFC4034][RFC3755]
DHCID 49 DHCID [RFC4701]
NSEC3 50 NSEC3 [RFC5155]
NSEC3PARAM 51 NSEC3PARAM [RFC5155]
TLSA 52 TLSA [RFC6698]
SMIMEA 53 S/MIME cert association [RFC8162] SMIMEA/smimea-completed-template 2015-12-01
Unassigned 54
HIP 55 Host Identity Protocol [RFC8005]
NINFO 56 NINFO [Jim_Reid] NINFO/ninfo-completed-template 2008-01-21
RKEY 57 RKEY [Jim_Reid] RKEY/rkey-completed-template 2008-01-21
TALINK 58 Trust Anchor LINK [Wouter_Wijngaards] TALINK/talink-completed-template 2010-02-17
CDS 59 Child DS [RFC7344] CDS/cds-completed-template 2011-06-06
CDNSKEY 60 DNSKEY(s) the Child wants reflected in DS [RFC7344] 2014-06-16
OPENPGPKEY 61 OpenPGP Key [RFC7929] OPENPGPKEY/openpgpkey-completed-template 2014-08-12
CSYNC 62 Child-To-Parent Synchronization [RFC7477] 2015-01-27
ZONEMD 63 message digest for DNS zone [draft-wessels-dns-zone-digest] ZONEMD/zonemd-completed-template 2018-12-12
Unassigned 64-98
SPF 99 [RFC7208]
UINFO 100 [IANA-Reserved]
UID 101 [IANA-Reserved]
GID 102 [IANA-Reserved]
UNSPEC 103 [IANA-Reserved]
NID 104 [RFC6742] ILNP/nid-completed-template
L32 105 [RFC6742] ILNP/l32-completed-template
L64 106 [RFC6742] ILNP/l64-completed-template
LP 107 [RFC6742] ILNP/lp-completed-template
EUI48 108 an EUI-48 address [RFC7043] EUI48/eui48-completed-template 2013-03-27
EUI64 109 an EUI-64 address [RFC7043] EUI64/eui64-completed-template 2013-03-27
Unassigned 110-248
TKEY 249 Transaction Key [RFC2930]
TSIG 250 Transaction Signature [RFC2845]
IXFR 251 incremental transfer [RFC1995]
AXFR 252 transfer of an entire zone [RFC1035][RFC5936]
MAILB 253 mailbox-related RRs (MB, MG or MR) [RFC1035]
MAILA 254 mail agent RRs (OBSOLETE - see MX) [RFC1035]
* 255 A request for some or all records the server has available [RFC1035][RFC6895][RFC8482]
URI 256 URI [RFC7553] URI/uri-completed-template 2011-02-22
CAA 257 Certification Authority Restriction [RFC-ietf-lamps-rfc6844bis-07] CAA/caa-completed-template 2011-04-07
AVC 258 Application Visibility and Control [Wolfgang_Riedel] AVC/avc-completed-template 2016-02-26
DOA 259 Digital Object Architecture [draft-durand-doa-over-dns] DOA/doa-completed-template 2017-08-30
AMTRELAY 260 Automatic Multicast Tunneling Relay [draft-ietf-mboned-driad-amt-discovery] AMTRELAY/amtrelay-completed-template 2019-02-06
Unassigned 261-32767
TA 32768 DNSSEC Trust Authorities [Sam_Weiler][http://cameo.library.cmu.edu/][ Deploying DNSSEC Without a Signed Root. Technical Report 1999-19, Information Networking Institute, Carnegie Mellon University, April 2004.] 2005-12-13
DLV 32769 DNSSEC Lookaside Validation [RFC4431]
Unassigned 32770-65279
Private use 65280-65534
Reserved 65535

DNS OpCodes

Registration Procedure(s)
Standards Action
Reference
[RFC6895][RFC1035]
Available Formats

CSV
OpCode Name Reference
0 Query [RFC1035]
1 IQuery (Inverse Query, OBSOLETE) [RFC3425]
2 Status [RFC1035]
3 Unassigned
4 Notify [RFC1996]
5 Update [RFC2136]
6 DNS Stateful Operations (DSO) [RFC8490]
7-15 Unassigned

DNS RCODEs

Reference
[RFC6895][RFC1035]
Available Formats

CSV
Range Registration Procedures
0-3840 IETF Review
3841-4095 Private Use
4096-65534 IETF Review
65535 Reserved (Standards Action)
RCODE Name Description Reference
0 NoError No Error [RFC1035]
1 FormErr Format Error [RFC1035]
2 ServFail Server Failure [RFC1035]
3 NXDomain Non-Existent Domain [RFC1035]
4 NotImp Not Implemented [RFC1035]
5 Refused Query Refused [RFC1035]
6 YXDomain Name Exists when it should not [RFC2136][RFC6672]
7 YXRRSet RR Set Exists when it should not [RFC2136]
8 NXRRSet RR Set that should exist does not [RFC2136]
9 NotAuth Server Not Authoritative for zone [RFC2136]
9 NotAuth Not Authorized [RFC2845]
10 NotZone Name not contained in zone [RFC2136]
11 DSOTYPENI DSO-TYPE Not Implemented [RFC8490]
12-15 Unassigned
16 BADVERS Bad OPT Version [RFC6891]
16 BADSIG TSIG Signature Failure [RFC2845]
17 BADKEY Key not recognized [RFC2845]
18 BADTIME Signature out of time window [RFC2845]
19 BADMODE Bad TKEY Mode [RFC2930]
20 BADNAME Duplicate key name [RFC2930]
21 BADALG Algorithm not supported [RFC2930]
22 BADTRUNC Bad Truncation [RFC4635]
23 BADCOOKIE Bad/missing Server Cookie [RFC7873]
24-3840 Unassigned
3841-4095 Reserved for Private Use [RFC6895]
4096-65534 Unassigned
65535 Reserved, can be allocated by Standards Action [RFC6895]

AFSDB RR Subtype

Registration Procedure(s)
Registry closed per [RFC6895]
Reference
[RFC6895][RFC1035]
Available Formats

CSV
Decimal Hexadecimal Description Reference
0 0x0000 Reserved; registry closed [RFC6895]
1 0x0001 Andrews File Service v3.0 Location Service [RFC1183]
2 0x0002 DCE/NCA root cell directory node [RFC1183]
3-65279 0x0003-0xFEFF Not allocated; registry closed
65280-65534 0xFF00-0xFFFE Reserved for Private Use [RFC6895]
65535 0xFFFF Reserved; registry closed [RFC6895]

DHCID RR Identifier Type Codes

Registration Procedure(s)
Standards Action
Expert(s)
Olafur Gudmundsson
Reference
[RFC4701]
Note
Registration rules to be as follows:
      
New DHCID RR type codes are tentatively assigned after the specification for the 
associated type code, published as an Internet Draft, has received expert review 
by a designated expert. The final assignment of DHCID RR type codes is through 
Standards Action, as defined in [RFC2434].
Available Formats

CSV
Identifier Type Code Identifier Reference
0x0000 The 1-octet 'htype' followed by 'hlen' octets of 'chaddr' from a DHCPv4 client's DHCPREQUEST. [RFC4701]
0x0001 The data octets (i.e., the Type and Client-Identifier fields) from a DHCPv4 client's Client Identifier option. [RFC4701]
0x0002 The client's DUID (i.e., the data octets of a DHCPv6 client's Client Identifier option or the DUID field from a DHCPv4 client's Client Identifier option). [RFC4701]
0x0003-0xFFFE Unassigned [RFC4701]
0xFFFF Reserved [RFC4701]

DHCID RR Digest Type Codes

Registration Procedure(s)
Standards Action
Reference
[RFC4701]
Available Formats

CSV
Digest Type Code Description Reference
0 Reserved [RFC4701]
1 SHA-256 [RFC4701]
2-255 Unassigned

DNS Label Types

Registration Procedure(s)
Standards Action
Reference
[RFC6891]
Note
The top 2 bits of the first byte of an DNS label indicate the type of label.
Available Formats

CSV
Value Type Status Reference
0 0 Normal label lower 6 bits is the length of the label Standard [RFC1035]
1 1 Compressed label the lower 6 bits and the 8 bits from next octet form a pointer to the compression target. Standard [RFC1035]
0 1 Extended label type the lower 6 bits of this type (section 3) indicate the type of label in use Proposed [RFC6891]
0 1 0 0 0 0 0 1 Binary Label Historic [RFC3364][RFC3363][RFC2673][RFC6891]
0 1 1 1 1 1 1 1 Reserved for future expansion. Proposed [RFC6891]
1 0 Unallocated

DNS EDNS0 Option Codes (OPT)

Expert(s)
Olafur Gudmundsson
Reference
[RFC6891][RFC Errata 3604]
Note
Registrations made by standards-track documents are listed as "Standard," 
and by non-standards-track documents as "Optional." Registrations for 
which there are no final specifications are listed as "On-Hold."
Available Formats

CSV
Range Registration Procedures
1-65000 Expert Review
65001-65534 Local/Experimental Use
Value Name Status Reference
0 Reserved [RFC6891]
1 LLQ On-hold [http://files.dns-sd.org/draft-sekar-dns-llq.txt]
2 UL On-hold [http://files.dns-sd.org/draft-sekar-dns-ul.txt]
3 NSID Standard [RFC5001]
4 Reserved [draft-cheshire-edns0-owner-option]
5 DAU Standard [RFC6975]
6 DHU Standard [RFC6975]
7 N3U Standard [RFC6975]
8 edns-client-subnet Optional [RFC7871]
9 EDNS EXPIRE Optional [RFC7314]
10 COOKIE Standard [RFC7873]
11 edns-tcp-keepalive Standard [RFC7828]
12 Padding Standard [RFC7830]
13 CHAIN Standard [RFC7901]
14 edns-key-tag Optional [RFC8145]
15 Unassigned
16 EDNS-Client-Tag Optional [draft-bellis-dnsop-edns-tags]
17 EDNS-Server-Tag Optional [draft-bellis-dnsop-edns-tags]
18-26945 Unassigned
26946 DeviceID Optional [https://docs.umbrella.com/developer/networkdevices-api/identifying-dns-traffic2][Brian_Hartvigsen]
26947-65000 Unassigned
65001-65534 Reserved for Local/Experimental Use [RFC6891]
65535 Reserved for future expansion [RFC6891]

DNS Header Flags

Registration Procedure(s)
Standards Action
Reference
[RFC6895][RFC1035]
Note
In DNS query header there is a flag field in the second 16 bit word in 
query from bit 5 through bit 11 ([RFC1035] section 4.1.1)
Available Formats

CSV
Bit Flag Description Reference
bit 5 AA Authoritative Answer [RFC1035]
bit 6 TC Truncated Response [RFC1035]
bit 7 RD Recursion Desired [RFC1035]
bit 8 RA Recursion Available [RFC1035]
bit 9 Reserved
bit 10 AD Authentic Data [RFC4035][RFC6840][RFC Errata 4924]
bit 11 CD Checking Disabled [RFC4035][RFC6840][RFC Errata 4927]

EDNS Header Flags (16 bits)

Registration Procedure(s)
Standards Action
Reference
[RFC6891]
Available Formats

CSV
Bit Flag Description Reference
Bit 0 DO DNSSEC answer OK [RFC4035][RFC3225][RFC6840][RFC Errata 4928]
Bit 1-15 Reserved

EDNS version Number (8 bits)

Registration Procedure(s)
Standards Action
Reference
[RFC6891]
Available Formats

CSV
Range Description Reference
0 EDNS version 0 [RFC6891]
1-255 Unassigned

Child Synchronization (CSYNC) Flags

Registration Procedure(s)
Standards Action
Reference
[RFC7477]
Available Formats

CSV
Bit Flag Description Reference
0 immediate Immediately process this CSYNC record. [RFC7477, Section 3]
1 soaminimum Require a SOA serial number greater than the one specified. [RFC7477, Section 2.1.1.1]
2-15 Unassigned

Underscored and Globally Scoped DNS Node Names

Registration Procedure(s)
Expert Review
Expert(s)
Frederico A C Neves
Reference
[RFC8552]
Available Formats

CSV
RR Type _NODE NAME Reference
* _example [RFC8552, Section 4.1.4]
NULL _ta-* [2] [RFC8145]
OPENPGPKEY _openpgpkey [RFC7929]
SMIMEA _smimecert [RFC8162]
SRV _dccp [RFC2782]
SRV _http [RFC4386]
SRV _ipv6 [RFC5026]
SRV _ldap [RFC4386]
SRV _ocsp [RFC4386]
SRV _sctp [RFC2782]
SRV _sip [RFC5509]
SRV _tcp [RFC2782]
SRV _udp [RFC2782]
SRV _xmpp [RFC3921]
TLSA _dane [RFC7671]
TLSA _sctp [RFC6698]
TLSA _tcp [RFC6698]
TLSA _udp [RFC6698]
TXT _acme-challenge [RFC8555]
TXT _dmarc [RFC7489]
TXT _domainkey [RFC6376]
TXT _mta-sts [RFC8461]
TXT _spf [RFC7208]
TXT _sztp [RFC8572]
TXT _tcp [RFC6763]
TXT _udp [RFC6763]
TXT _vouch [RFC5518]
URI _acct [RFC6118]
URI _dccp [RFC7566]
URI _email [RFC6118]
URI _ems [RFC6118]
URI _fax [RFC6118]
URI _ft [RFC6118]
URI _h323 [RFC6118]
URI _iax [RFC6118]
URI _ical-access [RFC6118]
URI _ical-sched [RFC6118]
URI _ifax [RFC6118]
URI _im [RFC6118]
URI _mms [RFC6118]
URI _pres [RFC6118]
URI _pstn [RFC6118]
URI _sctp [RFC6118]
URI _sip [RFC6118]
URI _sms [RFC6118]
URI _tcp [RFC6118]
URI _udp [RFC6118]
URI _unifmsg [RFC6118]
URI _vcard [RFC6118]
URI _videomsg [RFC6118]
URI _voice [RFC6118]
URI _voicemsg [RFC6118]
URI _vpim [RFC6118]
URI _web [RFC6118]
URI _xmpp [RFC6118]

DSO Type Codes

Expert(s)
Ted Lemon, Sara Dickinson, John Dickinson
Reference
[RFC8490]
Available Formats

CSV
Range Registration Procedures
0x0004-0x003F Standards Action
0x0040-0xF7FF Expert Review
0xF800-0xFBFF Experimental/Local Use
0xFC00-0xFFFF Standards Action
Type Name Early Data Status Reference
0x0000 Reserved NO Standards Track [RFC8490]
0x0001 KeepAlive OK Standards Track [RFC8490]
0x0002 RetryDelay NO Standards Track [RFC8490]
0x0003 EncryptionPadding NA Standards Track [RFC8490]
0x0004-0x003F Unassigned, reserved for DSO session-management TLVs NO
0x0040-0xF7FF Unassigned NO
0xF800-0xFBFF Reserved for Experimental/Local Use NO [RFC8490]
0xFC00-0xFFFF Reserved for future expansion NO

People

ID Name Contact URI Last Updated
[Brian_Hartvigsen] Brian Hartvigsen mailto:bhartvig&cisco.com 2016-12-09
[Donald_E_Eastlake] Donald E. Eastlake, III mailto:d3e3e3&gmail.com 1997-11
[George_Barwood] George Barwood mailto:george.barwood&blueyonder.co.uk 2011-06-06
[Jim_Reid] Jim Reid mailto:jim&telnic.org 2008-01-21
[Michael_Patton] Michael Patton mailto:map&bbn.com 1995-06
[Patrik_Faltstrom] Patrik Fältström mailto:paf&frobbit.se 2015-01-05
[Phillip_Hallam_Baker] Phillip Hallam-Baker mailto:phill&hallambaker.com 2011-04-07
[Sam_Weiler] Sam Weiler mailto:weiler+iana&tislabs.com 2005-12
[Wolfgang_Riedel] Wolfgang Riedel mailto:wolfgang&cisco.com 2016-02-26
[Wouter_Wijngaards] Wouter Wijngaards mailto:wouter&nlnetlabs.nl 2010-02-17

Footnotes

[1] 
In [RFC1002], two types are defined.  It is not clear that these
are in use, though if so their assignment does conflict with those 
above.

NB      32      NetBIOS general Name Service
NBSTAT  33      NetBIOS NODE STATUS
[2] 
From [RFC8552, Section 4.1.3 _ta]:
      
Under the NULL RR, the entry "_ta-*" denotes all node names beginning
with the string "_ta-*". It does NOT refer to a DNS wildcard
specification.