On Fri, 12 Aug 2005, johnp wrote:
* the TXT and SPF RRs can get out of sync due to TTLs being different.
Therefore, we should allow implementations to freely choose which
record they want to use.
No, please don't make this change. The appropriate thing is to specify
instead that TXT and SPF RRs dns records MUST have the same TTL.
Given that we are now committed to moving over to the type99 SPF record,
the spec should say that MTA's SHOULD check for the type99 record, and
MAY check for a TXT record if a type99 record does not exist. That solves
all the problems of conflicting records.
That is fine and your reasoning for such wording is good.
I am basing this on the premise that anyone who publishes a type99 record
will either:
1. be publishing for the first time and therefore no other record will
exist
or
2. be publishing the type99 as an "update" in his zonefile, and it will
contain the latest and more accurate spf record. If he omits to delete
the old TXT record, MTA's should *not* look at it in favour of the type99
record.
Slainte,
JohnP
--
William Leibzon
Elan Networks
william(_at_)elan(_dot_)net