ietf
[Top] [All Lists]

Re: Last Call: SMTP Service Extension for Content Negotiation to Proposed Standard

2002-07-03 00:04:01
First, let me say that I haven't read the draft, and don't intend to.
So, if you want to ignore my comments (questions really) feel free.

Fascinating. Although your detailed understanding of how this works is fairly
far off the mark, you nevertheless have suggested a viable approach that I, at
least, hadn't considered.

But from what I have picked up from the (smallish) number of messages
from an even smaller set of people (no great surprise, fax is dead
technology, who cares???) on the ietf list in the past day or so, I
surmise that this protocol work something like the following.

At least part of the problem is that the potential use of this stuff extend far
past FAX.

It sounds as if what is being proposed is that the SMTP client
sends

      RCPT TO:<address> "I want 1200 dpi"     

It is more like "RCPT TO:<address> "tell me what address can handle:"

Then the SMTP server says

      250 OK

More like: "250 address can handle 1200 dpi".

...

If this is how it works, I don't understand why people are talking about
doing RSET?   Surely the protocol isn't built in a way where the server
says "no" to a request, and yet still includes the address in its list
of recipients.

it can say "recipient accepted but capabilities are unknown"

Keith's operational plan can be done by sending RCPT TO (where he would
send RCAP) and terminating the sequence with RSET.   This way the RCPT
TO acts just as the RCAP would act in his model (as I understand it).
Sure, it isn't as clean by any means, and makes the server do a little
extra work, as it doesn't know the RCPT TO's aren't real ones when it
receives them, but as a trade off, it seems OK.

Ah. Using the first round of RCPT TOs as capabilities checks only and sending
the RSET unconditionally is really quite cute. It still has the added
complexity of having multiple commands per recipient, but now it is the same
command repeated, which eliminates a bunch of the edge conditions and makes the
silly states very silly indeed.

Others who prefer just to send and see what arrives, just do that, and
it all works the way they expect, with down grading, so the data only
ever needs to be sent once, or with separation of capabilities in the
cases (I am guessing this probably doesn't happen often, and most times
a server will offer the same capabilities to all addresses it can handle?)

I suspect there will be cases where the capabilities will be the same and
others where they are quite different.

                                Ned



<Prev in Thread] Current Thread [Next in Thread>