Re: [Asrg] [1] Why SPAM is worse in SMTP than in other protocols

[Yakov Shafranovich <research@solidmatrix.com>]

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
-------
Yakov Shafranovich / asrg <at> shaftek.org
SolidMatrix Technologies, Inc. / research <at> solidmatrix.com
"Some lies are easier to believe than the truth" (Dune)
-------


_______________________________________________
Asrg mailing list
Asrg@ietf.org
https://www1.ietf.org/mailman/listinfo/asrg