TXT record
Kevin Darcy
Kenneth Porter wrote:
> I've seen mention of TXT records on the list recently, but have never
> encountered one. What are they for? (I know about SOA, NS, A, CNAME,
> PTR, MX, HOST, and LOC. Just not TXT.) Is there a doc somewhere (RFC?)
> that lists all the kinds of records and what they are?
As others have mentioned, TXT records just store arbitrary text data, and
their format is defined in RFC 1035. The only thing I'd add is that there
have been various proposals over the years to "structure" TXT records to
store various kinds of information (see generally RFC 1464, for moves in
that direction). The general consensus seems to be that this is a Bad
Idea. Those proposals have gone nowhere. Either the data is so important
and relevant that it deserves its own record type, or it doesn't belong
in DNS at all, more properly to be stored in an LDAP-accessible directory
or something like that. So if you're considering using TXT fields as a
kind of "meta-database" within the DNS database, I'd say follow the
received wisdom of the protocol gods and seriously consider using some
other repository instead (not that the received wisdom is always *right*,
of course, but it does bear serious consideration and respect). If you're
not considering any such thing, then at least this might help explain why
TXT records are extremely rare...
- Kevin
Kenneth Porter
On Tue, 02 Jan 2001 23:19:16 -0500, Kevin Darcy wrote:
>So if you're considering using TXT fields as a
>kind of "meta-database" within the DNS database, I'd say follow the
>received wisdom of the protocol gods and seriously consider using some
>other repository instead (not that the received wisdom is always *right*,
>of course, but it does bear serious consideration and respect). If you're
>not considering any such thing, then at least this might help explain why
>TXT records are extremely rare...
Earlier on the list I saw someone mention that hand-maintained zone
files had one benefit over DDNS: comments. I had seen the TXT records
mentioned so this made me wonder if they were suitable for storing
those comments in.
Jim Reid
Kenneth> Earlier on the list I saw someone mention that
Kenneth> hand-maintained zone files had one benefit over DDNS:
Kenneth> comments. I had seen the TXT records mentioned so this
Kenneth> made me wonder if they were suitable for storing those
Kenneth> comments in.
Not really, though it could be done. One problem is that each TXT
record will have a name, just like every other resource record in the
DNS. So unless you used standardised names for every potential
comment, you'd have to keep track of what names existed to "tag" each
of those comments. It would be hard to lookup some comment without
knowing its name. Keeping track of those comments and their names
would be even harder if they were being added and removed with DDNS.
Comments are usually only worthwhile when the zone file is maintained
by hand: "if the MX record below is changed in any way, the sky will
fall in"; "this name is needed till the end of the month for A User's
test of foobar"; that sort of thing. These reminders to the zone
administrator can't be applied so easily when a zone is under dynamic
control. The thing making the dynamic updates probably won't know
these comments exist or know their names for looking them up if they
were TXT records. Or figure out what those comments mean in respect
of the dynamic update they're about to do.
Bill Manning
%
%
% On Tue, 02 Jan 2001 23:19:16 -0500, Kevin Darcy wrote:
%
% >So if you're considering using TXT fields as a
% >kind of "meta-database" within the DNS database, I'd say follow the
% >received wisdom of the protocol gods and seriously consider using some
% >other repository instead (not that the received wisdom is always *right*,
% >of course, but it does bear serious consideration and respect). If you're
% >not considering any such thing, then at least this might help explain why
% >TXT records are extremely rare...
%
% Earlier on the list I saw someone mention that hand-maintained zone
% files had one benefit over DDNS: comments. I had seen the TXT records
% mentioned so this made me wonder if they were suitable for storing
% those comments in.
%
% Ken
% mailto:sh...@well.com
% http://www.sewingwitch.com/ken/
Yes they are. And with a nod to Kevin, the "protocol gods" created TXT
records and they are used extensivly. For folk that want to use LDAP
style hooks, there is always the NAPTR RR... much less used than TXT,
at least for now.
--bill
Kevin Darcy
Bill Manning wrote:
> %
> %
> % On Tue, 02 Jan 2001 23:19:16 -0500, Kevin Darcy wrote:
> %
> % >So if you're considering using TXT fields as a
> % >kind of "meta-database" within the DNS database, I'd say follow the
> % >received wisdom of the protocol gods and seriously consider using some
> % >other repository instead (not that the received wisdom is always *right*,
> % >of course, but it does bear serious consideration and respect). If you're
> % >not considering any such thing, then at least this might help explain why
> % >TXT records are extremely rare...
> %
> % Earlier on the list I saw someone mention that hand-maintained zone
> % files had one benefit over DDNS: comments. I had seen the TXT records
> % mentioned so this made me wonder if they were suitable for storing
> % those comments in.
> %
> % Ken
> % mailto:sh...@well.com
> % http://www.sewingwitch.com/ken/
>
> Yes they are. And with a nod to Kevin, the "protocol gods" created TXT
> records and they are used extensivly.
In small pockets and proprietary ways, perhaps, but less than 0.0004% of the
queries my Internet nameservers receive are TXT queries. In fact, the combined
total of queries I get for *obsolete* record types (MG, MAILB,
WKS) substantially exceeds the number of TXT queries I get on a regular basis.
I know it's only circumstantial evidence, but it just doesn't seem like TXT is
very popular. YMMV.
- Kevin
D. J. Bernstein
Jim Reid writes:
> "this name is needed till the end of the month for A User's
> test of foobar";
tinydns lets you schedule records to appear or disappear in the future.
It automatically lowers the TTL as the disappearing time approaches.
http://cr.yp.to/djbdns/ad/server.html
http://cr.yp.to/djbdns/faq/tinydns.html
http://cr.yp.to/djbdns/install.html
---Dan
Barry Finkel
TXT records from one of my sniffer traces:
swip://aaa.bbb.ccc.ddd/
afp://aaa.bbb.ccc.ddd/?NAME=Conner_PPC_G3_300&ZONE=CMT%20205
Where "aaa.bbb.ccc.ddd" is an IP address.
----------------------------------------------------------------------
Barry S. Finkel
Electronics and Computing Technologies Division
Argonne National Laboratory Phone: +1 (630) 252-7277
9700 South Cass Avenue Facsimile:+1 (630) 252-9689
Building 221, Room B236 Internet: BSFi...@anl.gov
Argonne, IL 60439-4844 IBMMAIL: I1004994