Roger Moser wrote:
tdlc.com. 3600 IN TXT (
"v=spf1"
"a"
"mx"
"-all"
)
--wayne <wayne(_at_)midwestcs(_dot_)com> wrote:
However, we are not talking about multiple RRs here, we are talking
about multiple substrings on a single TXT RR. The last time I
checked, I could find nothing in the RFCs that guarenteed that the
substrings will not be rearranged, but in practice, I know of no cases
where the order is not preserved.
For some reason I read this type of record (which I first saw used in
MS-CID) and I assumed that the zone file would be read in by a server such
as bind, and would be sent as a single string. I don't think there are
really such things as multiple substrings in a TXT record once it is sent
over the wire to a requester - I believe it will be folded to a single long
string in the response (and probably in the transfer to a secondary also).
As used by MS-CID, they definitely were depending on NOT adding spaces,
since their example had the strings broken in the middle of a word (or some
xml thing that wouldn't work with spaces) if I remember right.
The implication of this is that breaking up a long string this way doesn't
make it more appropriate for sending, if the total is over $(PATHMTU) give
or take packet header and other fluff you will still have to fall back to
TCP to get it all. But it's a cool format for a file especially if you
add/reorder stuff often.
--
Greg Connor <gconnor(_at_)nekodojo(_dot_)org>