"John Leslie" <john(_at_)jlc(_dot_)net> commented:
John Glube <jbglube(_at_)sympatico(_dot_)ca> wrote:
"'John Leslie'" <john(_at_)jlc(_dot_)net> [wrrte:]
<snip>
* Have we lost the potential optimization which was
previously available?
I'm not clear what "optimization" you mean, but we've probably
lost it.
* Does the optimization suggested by Chris in his note to
Margaret, based on his offline discussion with Mark fully
replace this earlier optimization?
I'm not sure I understand what you refer to here. The obvious
sentence is:
]
] The optimization derived from using MAIL-FROM is the opportunity to
] fetch and start testing the record, in the hope that, when the PRA
] is eventually determined, the correct record is found to have been
] used.
The wording above is my understanding / interpretation of the optimisation
described by Mark Lentczner in his pseudo-code in
http://www.imc.org/ietf-mxcomp/mail-archive/msg03230.html
and which is applicable when no SUBMITTER has been used.
Inspect carefully his use of test 'r2' and note that this test result cannot be
acted upon until after the PRA is available and the initial 'guess' has been
proved correct.
This seems to imply that sender-ID checks could be run against
the MAIL-FROM when there is no submitter _before_ accepting the DATA.
I don't believe this is recommended in any of the current MARID I-Ds
(though it isn't actually prohibited).
The potential for saving any appreciable bandwidth escapes me,
unless we're talking about serious tar-pitting, which IMHO is quite
out of scope for MARID discussions.
All I believe it can save is time - the record can be being fetched from DNS and
evaluated in parallel with the SMTP DATA phase.
If it turns out that MAIL-FROM != PRA, bandwidth (and DNS service resource) will
have been wasted, as the first test result will be discarded.
Somebody may have an opinion on whether this replaces the earlier
optimization, but I certainly don't.
As I understand it, the central reason for introducing SUBMITTER was to give
Sender-ID the opportunity of matching the SPF optimisation of being able to
reject some messages before the SMTP DATA phase - saving bandwidth. I presume
this is what you refer to as the 'earlier optimisation'.
If no SUBMITTER is used, I believe Sender-ID must always proceed to the DATA
phase, as this is when the information defining the PRA is supplied.
<snip>
HTH
Chris Haynes