Domain Name System (DNS) Parameters

Last Updated
2026-08-28
Available Formats

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HTML
TXT

Registries Included Below

DNS CLASSes

Expert(s)
Petr Špaček, Ladislav Lhotka
Reference
[RFC 6895][RFC 9108]
Note
As noted in [RFC 6762], 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.
Note
When this registry is modified, the YANG module [iana-dns-class-rr-type] 
must be updated as defined in [RFC 9108].
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 [RFC 6895]
1 0x0001 Internet (IN) [RFC 1035]
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 [RFC 2136]
255 0x00FF QCLASS * (ANY) [RFC 1035]
256-65279 0x0100-0xFEFF Unassigned
65280-65534 0xFF00-0xFFFE Reserved for Private Use [RFC 6895]
65535 0xFFFF Reserved [RFC 6895]

Resource Record (RR) TYPEs

Expert(s)
Roy Arends, Frederico AC Neves, Ólafur Guðmundsson, Ray Bellis
Reference
[RFC 6895][RFC 1035][RFC 9108]
Note
When this registry is modified, the YANG module [iana-dns-class-rr-type] 
must be updated as defined in [RFC 9108].
Available Formats

CSV
Decimal Hex Registration Procedures Note
0 0x0000 RRTYPE zero is used as a special indicator for the SIG RR [RFC 2931], [RFC 4034] and in other circumstances and must never be allocated for ordinary use.
1-127 0x0000-0x007F Expert Review (see mailing list information in [RFC 6895]) or Standards Action data TYPEs
128-255 0x0080-0x00FF Expert Review (see mailing list information in [RFC 6895]) or Standards Action Q TYPEs, Meta TYPEs
256-61439 0x0100-0xEFFF Expert Review (see mailing list information in [RFC 6895]) 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
Reserved 0 [RFC 6895] 2021-03-08
A 1 a host address [RFC 1035]
NS 2 an authoritative name server [RFC 1035]
MD 3 a mail destination (OBSOLETE - use MX) [RFC 1035]
MF 4 a mail forwarder (OBSOLETE - use MX) [RFC 1035]
CNAME 5 the canonical name for an alias [RFC 1035]
SOA 6 marks the start of a zone of authority [RFC 1035]
MB 7 a mailbox domain name (EXPERIMENTAL) [RFC 1035]
MG 8 a mail group member (EXPERIMENTAL) [RFC 1035]
MR 9 a mail rename domain name (EXPERIMENTAL) [RFC 1035]
NULL 10 a null RR (EXPERIMENTAL) [RFC 1035]
WKS 11 a well known service description [RFC 1035]
PTR 12 a domain name pointer [RFC 1035]
HINFO 13 host information [RFC 1035]
MINFO 14 mailbox or mail list information [RFC 1035]
MX 15 mail exchange [RFC 1035]
TXT 16 text strings [RFC 1035]
RP 17 for Responsible Person [RFC 1183]
AFSDB 18 for AFS Data Base location [RFC 1183][RFC 5864]
X25 19 for X.25 PSDN address [RFC 1183]
ISDN 20 for ISDN address [RFC 1183]
RT 21 for Route Through [RFC 1183]
NSAP 22 for NSAP address, NSAP style A record (DEPRECATED) [RFC 1706][Moving TPC.INT and NSAP.INT infrastructure domains to historic]
NSAP-PTR 23 for domain name pointer, NSAP style (DEPRECATED) [RFC 1706][Moving TPC.INT and NSAP.INT infrastructure domains to historic]
SIG 24 for security signature [RFC 2536][RFC 2931][RFC 3110][RFC 4034]
KEY 25 for security key [RFC 2536][RFC 2539][RFC 3110][RFC 4034]
PX 26 X.400 mail mapping information [RFC 2163]
GPOS 27 Geographical Position [RFC 1712]
AAAA 28 IP6 Address [RFC 3596]
LOC 29 Location Information [RFC 1876]
NXT 30 Next Domain (OBSOLETE) [RFC 2535][RFC 3755]
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][RFC 2782]
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 [RFC 3403]
KX 36 Key Exchanger [RFC 2230]
CERT 37 CERT [RFC 4398]
A6 38 A6 (OBSOLETE - use AAAA) [RFC 2874][RFC 3226][RFC 6563]
DNAME 39 DNAME [RFC 6672]
SINK 40 SINK [Donald_E_Eastlake][draft-eastlake-kitchen-sink-02] 1997-11
OPT 41 OPT [RFC 3225][RFC 6891]
APL 42 APL [RFC 3123]
DS 43 Delegation Signer [RFC 4034]
SSHFP 44 SSH Key Fingerprint [RFC 4255]
IPSECKEY 45 IPSECKEY [RFC 4025]
RRSIG 46 RRSIG [RFC 4034]
NSEC 47 NSEC [RFC 4034][RFC 9077]
DNSKEY 48 DNSKEY [RFC 4034]
DHCID 49 DHCID [RFC 4701]
NSEC3 50 NSEC3 [RFC 5155][RFC 9077]
NSEC3PARAM 51 NSEC3PARAM [RFC 5155]
TLSA 52 TLSA [RFC 6698]
SMIMEA 53 S/MIME cert association [RFC 8162] SMIMEA/smimea-completed-template 2015-12-01
Unassigned 54
HIP 55 Host Identity Protocol [RFC 8005]
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 [RFC 7344] CDS/cds-completed-template 2011-06-06
CDNSKEY 60 DNSKEY(s) the Child wants reflected in DS [RFC 7344] 2014-06-16
OPENPGPKEY 61 OpenPGP Key [RFC 7929] OPENPGPKEY/openpgpkey-completed-template 2014-08-12
CSYNC 62 Child-To-Parent Synchronization [RFC 7477] 2015-01-27
ZONEMD 63 Message Digest Over Zone Data [RFC 8976] ZONEMD/zonemd-completed-template 2018-12-12
SVCB 64 General-purpose service binding [RFC 9460] SVCB/svcb-completed-template 2020-06-30
HTTPS 65 SVCB-compatible type for use with HTTP [RFC 9460] HTTPS/https-completed-template 2020-06-30
DSYNC 66 Endpoint discovery for delegation synchronization [RFC 9859] DSYNC/dsync-completed-template 2024-12-10
HHIT 67 Hierarchical Host Identity Tag [RFC 9886] HHIT/hhit-completed-template 2025-05-20
BRID 68 UAS Broadcast Remote Identification [RFC 9886] BRID/brid-completed-template 2025-05-20
UNECE 69 Value coded per a UNECE Recommendation [draft-woodcock-faltstrom-external-registry-rrtypes-00] UNECE/unece-completed-template 2026-08-20
ISO 70 Value coded per an ISO standard [draft-woodcock-faltstrom-external-registry-rrtypes-00] ISO/iso-completed-template 2026-08-20
Unassigned 71-98
SPF 99 [RFC 7208]
UINFO 100 [IANA-Reserved]
UID 101 [IANA-Reserved]
GID 102 [IANA-Reserved]
UNSPEC 103 [IANA-Reserved]
NID 104 [RFC 6742] ILNP/nid-completed-template
L32 105 [RFC 6742] ILNP/l32-completed-template
L64 106 [RFC 6742] ILNP/l64-completed-template
LP 107 [RFC 6742] ILNP/lp-completed-template
EUI48 108 an EUI-48 address [RFC 7043] EUI48/eui48-completed-template 2013-03-27
EUI64 109 an EUI-64 address [RFC 7043] EUI64/eui64-completed-template 2013-03-27
Unassigned 110-127
NXNAME 128 NXDOMAIN indicator for Compact Denial of Existence [RFC 9824] NXNAME/nxname-completed-template 2024-07-18
Unassigned 129-248
TKEY 249 Transaction Key [RFC 2930]
TSIG 250 Transaction Signature [RFC 8945]
IXFR 251 incremental transfer [RFC 1995]
AXFR 252 transfer of an entire zone [RFC 1035][RFC 5936]
MAILB 253 mailbox-related RRs (MB, MG or MR) [RFC 1035]
MAILA 254 mail agent RRs (OBSOLETE - see MX) [RFC 1035]
* 255 A request for some or all records the server has available [RFC 1035][RFC 6895][RFC 8482]
URI 256 URI [RFC 7553] URI/uri-completed-template 2011-02-22
CAA 257 Certification Authority Restriction [RFC 8659] 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-02] DOA/doa-completed-template 2017-08-30
AMTRELAY 260 Automatic Multicast Tunneling Relay [RFC 8777] AMTRELAY/amtrelay-completed-template 2019-02-06
RESINFO 261 Resolver Information as Key/Value Pairs [RFC 9606] RESINFO/resinfo-completed-template 2023-11-02
WALLET 262 Public wallet address [Paul_Hoffman] WALLET/wallet-completed-template 2024-06-21
CLA 263 BP Convergence Layer Adapter [draft-johnson-dns-ipn-cla-07] CLA/cla-completed-template 2024-07-25
IPN 264 BP Node Number [draft-johnson-dns-ipn-cla-07] IPN/ipn-completed-template 2024-07-25
Unassigned 265-32767
TA 32768 DNSSEC Trust Authorities [Sam_Weiler][ 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 (OBSOLETE) [RFC 8749][RFC 4431]
Unassigned 32770-65279
Private use 65280-65534
Reserved 65535

DNS OpCodes

Registration Procedure(s)
Standards Action
Reference
[RFC 6895][RFC 1035]
Available Formats

CSV
OpCode Name Reference
0 Query [RFC 1035]
1 IQuery (Inverse Query, OBSOLETE) [RFC 3425]
2 Status [RFC 1035]
3 Unassigned
4 Notify [RFC 1996]
5 Update [RFC 2136]
6 DNS Stateful Operations (DSO) [RFC 8490]
7-15 Unassigned

DNS RCODEs

Reference
[RFC 6895][RFC 1035]
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 [RFC 1035]
1 FormErr Format Error [RFC 1035]
2 ServFail Server Failure [RFC 1035]
3 NXDomain Non-Existent Domain [RFC 1035]
4 NotImp Not Implemented [RFC 1035]
5 Refused Query Refused [RFC 1035]
6 YXDomain Name Exists when it should not [RFC 2136][RFC 6672]
7 YXRRSet RR Set Exists when it should not [RFC 2136]
8 NXRRSet RR Set that should exist does not [RFC 2136]
9 NotAuth Server Not Authoritative for zone [RFC 2136]
9 NotAuth Not Authorized [RFC 8945]
10 NotZone Name not contained in zone [RFC 2136]
11 DSOTYPENI DSO-TYPE Not Implemented [RFC 8490]
12-15 Unassigned
16 BADVERS Bad OPT Version [RFC 6891]
16 BADSIG TSIG Signature Failure [RFC 8945]
17 BADKEY Key not recognized [RFC 8945]
18 BADTIME Signature out of time window [RFC 8945]
19 BADMODE Bad TKEY Mode [RFC 2930]
20 BADNAME Duplicate key name [RFC 2930]
21 BADALG Algorithm not supported [RFC 2930]
22 BADTRUNC Bad Truncation [RFC 8945]
23 BADCOOKIE Bad/missing Server Cookie [RFC 7873]
24-3840 Unassigned
3841-4095 Reserved for Private Use [RFC 6895]
4096-65534 Unassigned
65535 Reserved, can be allocated by Standards Action [RFC 6895]

AFSDB RR Subtype

Registration Procedure(s)
Registry closed per [RFC 6895]
Reference
[RFC 6895][RFC 1035]
Available Formats

CSV
Decimal Hexadecimal Description Reference
0 0x0000 Reserved; registry closed [RFC 6895]
1 0x0001 Andrews File Service v3.0 Location Service [RFC 1183]
2 0x0002 DCE/NCA root cell directory node [RFC 1183]
3-65279 0x0003-0xFEFF Not allocated; registry closed
65280-65534 0xFF00-0xFFFE Reserved for Private Use [RFC 6895]
65535 0xFFFF Reserved; registry closed [RFC 6895]

DHCID RR Identifier Type Codes

Registration Procedure(s)
Standards Action
Expert(s)
Ólafur Guðmundsson
Reference
[RFC 4701]
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 [RFC 2434].
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. [RFC 4701]
0x0001 The data octets (i.e., the Type and Client-Identifier fields) from a DHCPv4 client's Client Identifier option. [RFC 4701]
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). [RFC 4701]
0x0003-0xFFFE Unassigned [RFC 4701]
0xFFFF Reserved [RFC 4701]

DHCID RR Digest Type Codes

Registration Procedure(s)
Standards Action
Reference
[RFC 4701]
Available Formats

CSV
Digest Type Code Description Reference
0 Reserved [RFC 4701]
1 SHA-256 [RFC 4701]
2-255 Unassigned

DNS Label Types

Registration Procedure(s)
Standards Action
Reference
[RFC 6891]
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 [RFC 1035]
1 1 Compressed label the lower 6 bits and the 8 bits from next octet form a pointer to the compression target. Standard [RFC 1035]
0 1 Extended label type the lower 6 bits of this type (section 3) indicate the type of label in use Proposed [RFC 6891]
0 1 0 0 0 0 0 1 Binary Label Historic [RFC 3364][RFC 3363][RFC 2673][RFC 6891]
0 1 1 1 1 1 1 1 Reserved for future expansion. Proposed [RFC 6891]
1 0 Unallocated

DNS EDNS0 Option Codes (OPT)

Expert(s)
Ólafur Guðmundsson (primary), Frederico AC Neves (secondary), Ray Bellis (secondary), Roy Arends (secondary)
Reference
[RFC 6891][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 [RFC 6891]
1 LLQ Optional [RFC 8764]
2 Update Lease Standard [RFC 9664]
3 NSID Standard [RFC 5001]
4 Reserved [draft-cheshire-edns0-owner-option-00]
5 DAU Standard [RFC 6975]
6 DHU Standard [RFC 6975]
7 N3U Standard [RFC 6975]
8 edns-client-subnet Optional [RFC 7871]
9 EDNS EXPIRE Optional [RFC 7314]
10 COOKIE Standard [RFC 7873]
11 edns-tcp-keepalive Standard [RFC 7828]
12 Padding Standard [RFC 7830]
13 CHAIN Standard [RFC 7901]
14 edns-key-tag Optional [RFC 8145]
15 Extended DNS Error Standard [RFC 8914]
16 EDNS-Client-Tag Optional [draft-bellis-dnsop-edns-tags-01]
17 EDNS-Server-Tag Optional [draft-bellis-dnsop-edns-tags-01]
18 Report-Channel Standard [RFC 9567]
19 ZONEVERSION Standard [RFC 9660]
20 MQTYPE-Query Optional [RFC 10029]
21 MQTYPE-Response Optional [RFC 10029]
22 EDE-EXTRA-TEXT-LANGUAGE Optional [draft-muks-dns-filtering-05]
23 FILTERING-CONTACT Optional [draft-muks-dns-filtering-05]
24 FILTERING-ORGANIZATION Optional [draft-muks-dns-filtering-05]
25 FILTERING-DB Optional [draft-muks-dns-filtering-05]
26 Structured DNS Error Standard [RFC-ietf-dnsop-structured-dns-error-27]
27-20291 Unassigned
20292 Umbrella Ident Optional [https://developer.cisco.com/docs/cloud-security/#!integrating-network-devices/rdata-description][Cisco_CIE_DNS_team]
20293-26945 Unassigned
26946 DeviceID Optional [https://developer.cisco.com/docs/cloud-security/#!network-devices-getting-started/response-codes][Cisco_CIE_DNS_team]
26947-65000 Unassigned
65001-65534 Reserved for Local/Experimental Use [RFC 6891]
65535 Reserved for future expansion [RFC 6891]

DNS Header Flags

Registration Procedure(s)
Standards Action
Reference
[RFC 6895][RFC 1035]
Note
In DNS query header there is a flag field in the second 16 bit word in 
query from bit 5 through bit 11 ([RFC 1035] section 4.1.1)
Available Formats

CSV
Bit Flag Description Reference
bit 5 AA Authoritative Answer [RFC 1035]
bit 6 TC Truncated Response [RFC 1035]
bit 7 RD Recursion Desired [RFC 1035]
bit 8 RA Recursion Available [RFC 1035]
bit 9 Reserved
bit 10 AD Authentic Data [RFC 4035][RFC 6840][RFC Errata 4924]
bit 11 CD Checking Disabled [RFC 4035][RFC 6840][RFC Errata 4927]

EDNS Header Flags (16 bits)

Registration Procedure(s)
Standards Action
Reference
[RFC 6891]
Available Formats

CSV
Bit Flag Description Reference
Bit 0 DO DNSSEC answer OK [RFC 4035][RFC 3225][RFC 6840][RFC Errata 4928]
Bit 1 CO Compact Answers OK [RFC 9824]
Bit 2 DE Delegation Extensions (TEMPORARY - registered 2026-07-20, expires 2027-07-20) [draft-ietf-dnsop-delext-08]
Bit 3-15 Reserved

EDNS version Number (8 bits)

Registration Procedure(s)
Standards Action
Reference
[RFC 6891]
Available Formats

CSV
Range Description Reference
0 EDNS version 0 [RFC 6891]
1-255 Unassigned

Child Synchronization (CSYNC) Flags

Registration Procedure(s)
Standards Action
Reference
[RFC 7477]
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, Paul Wouters
Reference
[RFC 8552]
Available Formats

CSV
RR Type _NODE NAME Reference
* _example [RFC8552, Section 4.1.4]
CDNSKEY _signal [RFC 9615]
CDS _signal [RFC 9615]
DSYNC _dsync [RFC 9859]
HTTPS _https [RFC 9460]
NULL _ta-* [2] [RFC 8145]
OPENPGPKEY _openpgpkey [RFC 7929]
SMIMEA _smimecert [RFC 8162]
SRV _dccp [RFC 2782]
SRV _http [RFC 4386]
SRV _ipv6 [RFC 5026]
SRV _ldap [RFC 4386]
SRV _ocsp [RFC 4386]
SRV _sctp [RFC 2782]
SRV _sip [RFC 5509]
SRV _stun [RFC8489, Section 8.1]
SRV _stuns [RFC8489, Section 8.1]
SRV _tcp [RFC 2782]
SRV _turn [RFC8656, Section 4.1]
SRV _turns [RFC8656, Section 4.1]
SRV _udp [RFC 2782]
SRV _xmpp [RFC 3921]
SVCB _dns [RFC 9461]
TLSA _dane [RFC 7671]
TLSA _sctp [RFC 6698]
TLSA _tcp [RFC 6698]
TLSA _udp [RFC 6698]
TXT _x402 [draft-hawkins-x402-dns-discovery-01]
TXT _acme-challenge [RFC 8555]
TXT _dmarc [RFC 9989]
TXT _domainkey [RFC 6376]
TXT _er [RFC 9567]
TXT _for-sale [RFC 10023]
TXT _mta-sts [RFC 8461]
TXT _nnu-verification [https://nnu.us/specifications/nnu-domain-verification-1.0.txt]
TXT _spf [RFC 7208]
TXT _splitdns-challenge [RFC 9704]
TXT _sztp [RFC 8572]
TXT _tcp [RFC 6763]
TXT _tls [RFC 8460]
TXT _udp [RFC 6763]
TXT _validation-contactemail [https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.7.4.pdf]
TXT _validation-contactphone [https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.7.4.pdf]
TXT _vouch [RFC 5518]
URI _acct [RFC 7566][RFC Errata 7064]
URI _dccp [RFC 4340][RFC Errata 7066]
URI _email [RFC 6118]
URI _ems [RFC 6118]
URI _fax [RFC 6118]
URI _ft [RFC 6118]
URI _h323 [RFC 6118]
URI _iax [RFC 6315][RFC Errata 7065]
URI _ical-access [RFC 6118]
URI _ical-sched [RFC 6118]
URI _ifax [RFC 6118]
URI _im [RFC 6118]
URI _mms [RFC 6118]
URI _pres [RFC 6118]
URI _pstn [RFC 6118]
URI _sctp [RFC 4340][RFC Errata 7067]
URI _sip [RFC 6118]
URI _sms [RFC 6118]
URI _tcp [RFC 4340][RFC Errata 7068]
URI _udp [RFC 4340][RFC Errata 7068]
URI _unifmsg [RFC 6118]
URI _vcard [RFC 6118]
URI _videomsg [RFC 6118]
URI _voice [RFC 6118]
URI _voicemsg [RFC 6118]
URI _vpim [RFC 6118]
URI _web [RFC 6118]
URI _xmpp [RFC 6118]

DSO Type Codes

Expert(s)
Ted Lemon, Sara Dickinson, John Dickinson
Reference
[RFC 8490]
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 [RFC 8490]
0x0001 KeepAlive OK Standards Track [RFC 8490]
0x0002 RetryDelay NO Standards Track [RFC 8490]
0x0003 EncryptionPadding NA Standards Track [RFC 8490]
0x0004-0x003F Unassigned, reserved for DSO session-management TLVs NO
0x0040 SUBSCRIBE OK Standards Track [RF8765, Section 6.2]
0x0041 PUSH NO Standards Track [RF8765, Section 6.3]
0x0042 UNSUBSCRIBE NO Standards Track [RF8765, Section 6.4]
0x0043 RECONFIRM NO Standards Track [RF8765, Section 6.5]
0x0044-0xF7FF Unassigned NO
0xF800-0xFBFF Reserved for Experimental/Local Use NO [RFC 8490]
0xFC00-0xFFFF Reserved for future expansion NO

Extended DNS Error Codes

Reference
[RFC 8914]
Available Formats

CSV
Range Registration Procedures
0-49151 First Come First Served
49152-65535 Private Use
INFO-CODE Purpose Reference
0 Other Error [RFC8914, Section 4.1]
1 Unsupported DNSKEY Algorithm [RFC8914, Section 4.2]
2 Unsupported DS Digest Type [RFC8914, Section 4.3]
3 Stale Answer [RFC8914, Section 4.4][RFC 8767]
4 Forged Answer [RFC8914, Section 4.5]
5 DNSSEC Indeterminate [RFC8914, Section 4.6]
6 DNSSEC Bogus [RFC8914, Section 4.7]
7 Signature Expired [RFC8914, Section 4.8]
8 Signature Not Yet Valid [RFC8914, Section 4.9]
9 DNSKEY Missing [RFC8914, Section 4.10]
10 RRSIGs Missing [RFC8914, Section 4.11]
11 No Zone Key Bit Set [RFC8914, Section 4.12]
12 NSEC Missing [RFC8914, Section 4.13]
13 Cached Error [RFC8914, Section 4.14]
14 Not Ready [RFC8914, Section 4.15]
15 Blocked [RFC8914, Section 4.16]
16 Censored [RFC8914, Section 4.17]
17 Filtered [RFC8914, Section 4.18]
18 Prohibited [RFC8914, Section 4.19]
19 Stale NXDomain Answer [RFC8914, Section 4.20]
20 Not Authoritative [RFC8914, Section 4.21]
21 Not Supported [RFC8914, Section 4.22]
22 No Reachable Authority [RFC8914, Section 4.23]
23 Network Error [RFC8914, Section 4.24]
24 Invalid Data [RFC8914, Section 4.25]
25 Signature Expired before Valid [https://github.com/NLnetLabs/unbound/pull/604#discussion_r802678343][Willem_Toorop]
26 Too Early [RFC 9250]
27 Unsupported NSEC3 Iterations Value [RFC 9276]
28 Unable to conform to policy [draft-homburg-dnsop-codcp-00]
29 Synthesized [https://github.com/PowerDNS/pdns/pull/12334][Otto_Moerbeek]
30 Invalid Query Type [RFC 9824]
31 Rate Limited [draft-muks-dns-ede-rate-limited-02, Section 2]
32 Over Quota [draft-muks-dns-ede-rate-limited-02, Section 3]
33 Negative Trust Anchor [draft-farrokhi-dnsop-ede-nta-00]
34 New Delegation Only [draft-ietf-deleg-10]
35 Blocked by Upstream DNS Server [RFC-ietf-dnsop-structured-dns-error-27]
36-49151 Unassigned
49152-65535 Reserved for Private Use [RFC8914, Section 5.2]

EXTRA-TEXT JSON Names

Registration Procedure(s)
IETF Review
Reference
[RFC-ietf-dnsop-structured-dns-error-27]
Available Formats

CSV
JSON Name Field Meaning Description Reference
c contact The contact details of the IT/InfoSec team to report misclassified DNS filtering [RFC-ietf-dnsop-structured-dns-error-27, Section 4]
j justification UTF-8-encoded [RFC 5198] textual justification for a particular DNS filtering [RFC-ietf-dnsop-structured-dns-error-27, Section 4]
s sub-error Integer representing the sub-error code for this DNS filtering case [RFC-ietf-dnsop-structured-dns-error-27, Section 4]
o organization UTF-8-encoded human-friendly name of the organization that filtered this particular DNS query [RFC-ietf-dnsop-structured-dns-error-27, Section 4]
l language Indicates the language of the "j" and "o" fields as defined in [RFC 5646] [RFC-ietf-dnsop-structured-dns-error-27, Section 4]

Contact URI Schemes

Registration Procedure(s)
IETF Review
Reference
[RFC-ietf-dnsop-structured-dns-error-27]
Available Formats

CSV
Name Meaning Reference
tel Telephone Number [RFC 3966]
mailto Internet mail [RFC 6068]

Extended DNS Sub-Error Codes

Registration Procedure(s)
IETF Review
Reference
[RFC-ietf-dnsop-structured-dns-error-27]
Available Formats

CSV
Number Meaning EDE Codes Applicability Reference
0 Reserved Not used [RFC-ietf-dnsop-structured-dns-error-27, Section 6.1]
1 Malware "Blocked", "Blocked by Upstream DNS Server", "Filtered" [RFC5901, Section 5.5]
2 Phishing "Blocked", "Blocked by Upstream DNS Server", "Filtered" [RFC5901, Section 5.5]
3 Spam "Blocked", "Blocked by Upstream DNS Server", "Filtered" [RFC 4949]
4 Spyware "Blocked", "Blocked by Upstream DNS Server", "Filtered" [RFC 4949]
5 Network operator policy "Blocked" [RFC-ietf-dnsop-structured-dns-error-27, Section 6.2]
6 DNS operator policy "Blocked" [RFC-ietf-dnsop-structured-dns-error-27, Section 6.3]
7-255 Unassigned

ZONEMD Schemes

Expert(s)
Warren Kumari, Duane Wessels, Wes Hardaker
Reference
[RFC 8976]
Available Formats

CSV
Range Registration Procedures
1-239 Specification Required
240-254 Private Use
Value Description Mnemonic Reference
0 Reserved [RFC 8976]
1 Simple ZONEMD collation SIMPLE [RFC 8976]
2-239 Unassigned
240-254 Reserved for Private Use N/A [RFC 8976]
255 Reserved [RFC 8976]

ZONEMD Hash Algorithms

Expert(s)
Warren Kumari, Duane Wessels, Wes Hardaker
Reference
[RFC 8976]
Available Formats

CSV
Range Registration Procedures
1-239 Specification Required
240-254 Private Use
Value Description Mnemonic Reference
0 Reserved [RFC 8976]
1 SHA-384 SHA384 [RFC 8976]
2 SHA-512 SHA512 [RFC 8976]
3-239 Unassigned
240-254 Reserved for Private Use N/A [RFC 8976]
255 Reserved [RFC 8976]

DNS Server Cookie Methods

Expert(s)
Ondřej Surý, Donald Eastlake
Reference
[RFC 9018][RFC 7873]
Note
A Server Cookie method (construction and pseudorandom algorithm)
is determined by the Version in the first byte of the Cookie and by
the Cookie size. Server Cookie size is limited to the inclusive
range of 8 to 32 bytes.
Available Formats

CSV

DNS-over-QUIC Error Codes

Expert(s)
Sara Dickinson, Christian Huitema
Reference
[RFC 9250]
Available Formats

CSV
Range Registration Procedures
provisional (greater than 0x3f) Expert Review
provisional registration Date field update First Come First Served
permanent, 0x00-0x3f Standards Action or IESG Approval
permanent, greater than 0x3f Specification Required
Value Error Description Status Specification Date Contact
0x0 DOQ_NO_ERROR No error permanent [RFC9250, Section 4.3] 2022-04-01 [DPRIVE_WG]
0x1 DOQ_INTERNAL_ERROR Implementation error permanent [RFC9250, Section 4.3] 2022-04-01 [DPRIVE_WG]
0x2 DOQ_PROTOCOL_ERROR Generic protocol violation permanent [RFC9250, Section 4.3] 2022-04-01 [DPRIVE_WG]
0x3 DOQ_REQUEST_CANCELLED Request cancelled by client permanent [RFC9250, Section 4.3] 2022-04-01 [DPRIVE_WG]
0x4 DOQ_EXCESSIVE_LOAD Closing a connection for excessive load permanent [RFC9250, Section 4.3] 2022-04-01 [DPRIVE_WG]
0x5 DOQ_UNSPECIFIED_ERROR No error reason specified permanent [RFC9250, Section 4.3] 2022-04-01 [DPRIVE_WG]
0xd098ea5e DOQ_ERROR_RESERVED Alternative error code used for tests permanent [RFC9250, Section 4.3] 2022-04-01 [DPRIVE_WG]

DNS Catalog Zones Properties

Expert(s)
Peter Thomassen, Ondřej Surý, Willem Toorop
Reference
[RFC 9432]
Note
This registry applies to Catalog Zones schema version "2" as specified 
in [RFC 9432].
Available Formats

CSV
Range Registration Procedures
property prefix ends in the label "ext" Private Use
all other property prefixes Expert Review
Property Prefix Description Status Reference
zones List of member zones Standards Track [RFC 9432]
version Schema version Standards Track [RFC 9432]
coo Change of Ownership Standards Track [RFC 9432]
group Group Standards Track [RFC 9432]
*.ext Custom properties Private Use [RFC 9432]

DNS Resolver Information Keys

Registration Procedure(s)
Specification Required
Expert(s)
Tirumal Reddy, Mohamed Boucadair, Ben Schwartz
Reference
[RFC 9606]
Available Formats

CSV
Name Description Reference
qnamemin The presence of the key name indicates that QNAME minimisation is enabled. [RFC 9606]
exterr Lists the set of enabled extended DNS errors. It must be an INFO-CODE decimal value in the [Extended DNS Error Codes] registry. [RFC 9606]
infourl Provides a URL that points to unstructured resolver information that is used for troubleshooting. [RFC 9606]
deleg The presence of the key indicates that the DELEG protocol is supported. (TEMPORARY - registered 2026-08-24, expires 2027-08-24) [draft-ietf-deleg-11]

ZONEVERSION TYPE Values

Expert(s)
Hugo Salgado, Mauricio Vergara Ereche, Duane Wessels
Reference
[RFC 9660]
Available Formats

CSV
Range Registration Procedures
0-245 Specification Required
246-254 Private Use
255 Reserved
ZONEVERSION TYPE Mnemonic Reference
0 SOA-SERIAL [RFC 9660]
1-245 Unassigned
246-254 Reserved for Private Use [RFC 9660]
255 Reserved [RFC 9660]

DSYNC: Location of Synchronization Endpoints

Registration Procedure(s)
Expert Review
Expert(s)
Johan Stenstam, Peter Thomassen, John Levine
Reference
[RFC 9859]
Available Formats

CSV
RRtype Scheme (Mnemonic) Purpose Reference
0 Null scheme (no-op) [RFC 9859]
CDS 1 (NOTIFY) Delegation management [RFC 9859]
CSYNC 1 (NOTIFY) Delegation management [RFC 9859]
2-127 Unassigned
128-255 Reserved for Private Use [RFC 9859]

Contact Information

ID Name Contact URI Last Updated
[Cisco_CIE_DNS_team] Cisco CIE DNS team mailto:cie-eng.dns-team&cisco.com 2021-08-31
[Donald_E_Eastlake] Donald E. Eastlake, III mailto:d3e3e3&gmail.com 1997-11
[DPRIVE_WG] DPRIVE working group mailto:dns-privacy&ietf.org 2022-04-01
[Jim_Reid] Jim Reid mailto:jim&telnic.org 2008-01-21
[Michael_Patton] Michael Patton mailto:map&bbn.com 1995-06
[Otto_Moerbeek] Otto Moerbeek mailto:otto.moerbeek&powerdns.com 2023-03-29
[Paul_Hoffman] Paul Hoffman mailto:paul.hoffman&icann.org 2024-07-01
[Sam_Weiler] Sam Weiler mailto:weiler+iana&tislabs.com 2005-12
[Willem_Toorop] Willem Toorop mailto:willem&nlnetlabs.nl 2022-02-11
[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 [RFC 1002], 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.