Start of Authority - Obsolete Record Types

Obsolete Record Types

Progress has rendered obsolete some of the originally defined record-types. Of the records listed at IANA, some have limited use, for various reasons. Some are marked obsolete in the list, some are for very obscure services, some are for older versions of services, and some have special notes saying they are "not right".

  • Obsoleted by RFC 973: MD(3), MF (4), MAILA (254)
  • Records to publish mailing list subscriber lists in the DNS: MB(7), MG(8), MR(9), MINFO(14), MAILB (253). The intent, as specified by RFC 883, was for MB to replace the SMTP VRFY command, MG to replace the SMTP EXPN command, and MR to replace the "551 User Not Local" SMTP error. Later, RFC 2505 recommended that both the VRFY and EXPN commands be disabled, making the use of MB and MG unlikely to ever be adopted.
  • Declared "not to be relied upon" by RFC 1123 (with further information in RFC 1127): WKS(11)
  • Mistakes: NB(32), NBSTAT(33) (from RFC 1002); the numbers are now assigned to NIMLOC and SRV.
  • Obsoleted by RFC 1035: NULL(10) (RFC 883 defined "completion queries" (opcode 2 and maybe 3) which used this record, RFC 1035 later reassigned opcode 2 to be "status" and reserved opcode 3.)
  • Defined as part of early IPv6 but downgraded to experimental by RFC 3363: A6(38), Later downgraded to historic in RFC 6563.
  • Obsoleted by DNSSEC updates (RFC 3755): NXT(30). At the same time, the domain of applicability for KEY and SIG was also limited to not include DNSSEC use.
  • Part of the first version of DNSSEC (RFC 2065).
  • Not in current use by any notable application: HINFO(13), RP(17), X25(19), ISDN(20), RT(21), NSAP(22), NSAP-PTR(23), PX(26), EID(31), NIMLOC(32), ATMA(34), APL(42)
  • Defined by the Kitchen Sink internet draft, but never made it to RFC status: SINK(40)
  • A more limited early version of the LOC record: GPOS(27)
  • IANA reserved, no RFC documented them and support was removed from BIND in the early 90s: UINFO(100), UID(101), GID(102), UNSPEC(103)

RP(17) may be used for certain human-readable information regarding a different contact point for a specific host, subnet, or other domain level label separate than that used in the SOA record.

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