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SubjectRe: No more DoS
   Date: 	Fri, 22 Dec 2000 13:24:44 +1100 (CST)
From: Mike OConnor <>

I would like to point who ever is in charge of the TCP stack for
the linux kernel at a site which claims to have a method of
eliminate denial of service (DoS) attacks

With my limited unstanding of TCP and DoS attacks this would seem
to be the answer, instead of a work around.

These people claim that no connection state needs to be saved for the
beginning of the negotiation, and I claim this is unworkable because
it ignores TCP timestamps entirely.

Furthermore, it also cannot work because it makes retransmissions
of the SYN/ACK very non-workable. I suppose his TCP stack just hacks
around this by just waiting for the original client SYN to get
retransmitted or something like this. I question whether that can
even work reliably.

I think not holding onto any state for an incoming SYN is nothing but
a dream in any serious modern TCP implementation. It can be reduced,
but not eliminated. The former is what most modern stacks have done
to fight these problems.

David S. Miller
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