Re: SPF Records
- From: "Herb Martin" <news@xxxxxxxxxxxxxx>
- Date: Fri, 21 Apr 2006 09:02:49 -0500
"Ace Fekay [MVP]"
<PleaseSubstituteMyActualFirstName&LastNameHere@xxxxxxxxxxx> wrote in
message news:OQ2ReKoPGHA.2912@xxxxxxxxxxxxxxxxxxxxxxx
In news:1141242510.442963.132960@xxxxxxxxxxxxxxxxxxxxxxxxxxxx,
Carl R <carlrimmel@xxxxxxxxx> stated, which I commented on below:
I found RFC 1035. I defines DNS RR types, but it didn't specifically
mention length about any specific record, but it did say a "Name" can only
be 255. The text data in a TXT is a "name" by it's definition, as I read
from the article and noted below from RFC 1035:
http://www.faqs.org/rfcs/rfc1035.html
Maybe I can help.
If you write a TXT record (for SPF etc) that is too long
(and I forget the actual limit but generally make it fit
in the dialog width and you are ok) then you WILL get
truncated behavior -- if not in the console itself, in the
return value to client requests.
IF HOWEVER you (artificially) use your own line
breaks it seems to work for most all purposes.
There are also absolute limits beyond which at least
some clients and SPF processing software (that is
common) will blow up on your records.
The following (rather long) record works -- it is
LITERALLY 5 lines as shown:
v=spf1 ip4:64.202.167.0/24 ip4:64.202.189.0/24
ip4:64.202.166.0/24 ip4:64.202.165.0/24 ip4:64.202.163.0/24
ip4:68.178.144.60/31 include:in.spf.secureserver.net
include:spf.learnquick.com include:deleted.com
include:ak.learnquick.com ip4:68.178.144.167 -all
--
Herb Martin, MCSE, MVP
Accelerated MCSE
http://www.LearnQuick.Com
[phone number on web site]
=====================
2.3.4. Size limits
Various objects and parameters in the DNS have size limits. They are
listed below. Some could be easily changed, others are more
fundamental.
labels 63 octets or less
names 255 octets or less
TTL positive values of a signed 32 bit number.
UDP messages 512 octets or less
=====================
John had a point earlier on about keeping response records less than 512,
but that would be the total response of a query, meaning, if a query was
for an MX record, all the MX records for a zone will be returned. Hotmail
and Yahoo have over 512 in the response, but each record is barely a line
long. In this case, the TXT record is just that, a record, and has
limitations based on the RFC.
So, I would not bash Microsoft about this because they're just following
the RFCs, as are other DNS vendors. So I think you were a little quick to
point fingers without doing a little simple research on it to
prove/disprove it.
Ace
.
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