Markus Stumpf wrote:
On Sun, Dec 21, 2003 at 10:54:55AM -0500, Alan DeKok wrote:
...
Nonsense. Have you ever done any work with networks, or protocols?
You're always so easy with your "nonsense". And it's always easy for you
to try to discredit others by asking them "are you on crack or what?".
Maybe you should simply think before writing all those bullshit.
You just can't stand it if others have a different opinion that doesn't
match your - of course - unfailing point of (limited) view.
Lets cool it a bit.
When e.g. the ethernet stack gets a frame it doesn't care what the contents
is. The ethernet stack takes the packet, drops the envelope and hands
it off to the next stack. This looks at the content and dispatches it
e.g. to the IP stack handler. This drops the IP envelope and hands it
off to the next handler which decides whether to e.g. dispatch it to
TCP/UDP/ICMP. It is an explicit design goal of protocol stacks that the
higher level protocol doesn't have to know anything about the lower
level protocols to peer communicate with its partner and the lower
level protocol doesn't have to know anything about the
contents/data/encoding of the higher level protocol to transport it.
...
Lets step back for a second. We are comparing the SMTP protocol with
other protocols in order to determine which problems the SMTP protocol
has similar to other protocols, and see which solutions applied in other
protocols can help us here.
The point of contention here seems to be whether SMTP is intended to be
an end-to-end protocol (like a network layer protocol of the OSI model),
or a hop-to-hop protocol (like a link layer protocol). Obviously SMTP is
in reality is running above these layers on application layer, but we'll
ignore that for a second.
Now lets see section 2.1 of RFC 2821:
" In other words, message transfer can occur in a single connection
between the original SMTP-sender and the final SMTP-recipient, or can
occur in a series of hops through intermediary systems. In either
case, a formal handoff of responsibility for the message occurs: the
protocol requires that a server accept responsibility for either
delivering a message or properly reporting the failure to do so.
"
It seems from here that the SMTP protocol can either operate as an
end-to-end protocol or a hop-by-hop protocol. The RFC states that a
server must accept responsibility for the message if it is not the final
destination, which implies that each individual hop is independent of
each other. On the other hand, in many cases only one SMTP transaction
takes place between the originating ISP's MTA and the receiver ISP's MTA.
So what comes out from this, is that SMTP operates on a hop-by-hop
basis, which in many cases is end-to-end since there is only a single
hop to be done.
Now the question is, what can we, as a RG, learn from this? How is this
behavior helpful to stopping spam? What comparisons can we draw from
this behavior to other protocols?
Yakov
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Yakov Shafranovich / asrg <at> shaftek.org
SolidMatrix Technologies, Inc. / research <at> solidmatrix.com
"Some lies are easier to believe than the truth" (Dune)
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