From: "Eric S. Johansson" <esj(_at_)harvee(_dot_)org>
... The cost of sending e-mail on a low-end
machine will probably the only about 30 or 40 seconds per address ...
If a 25 MHz 80486 needs 30 seconds to compute a number, then a 3 GHz
P4 should need at most 150 milliseconds to compute the same value,
and probably less than 75 milliseconds. The ratio of clock speeds is
only 120X but has lots of other fancy stuff to make computations to
faster, particularly when all of the values can fit in the P4's (or
P-III's) vastly larger caches. (Never mind that the 486 had only the
off-chip caches).
150 ms, not to mention 75 ms is less than a single typical round trip
through the Internet. Getting the banner from a target SMTP server
needs 2 round trips. However, a serious bulk mailer will surely
overlap SMTP sessions.
A computer that is limited to sending 1 message every 150 ms will send
576,000 mail messages/day. Such computers cost less than $600 in
single quantities from retail stores, and a fraction of that if you
are willing to build your own "blade-like" servers. (Ok, you might
have to settle for 1 or 2 GHz CPUs that are only 90 times as fast as
low-end systems.)
One 5 KByte mail message in 150 ms needs about 40 KByte/sec of bandwidth
after you add SMTP, TCP, IP, and link-layer overhead.
Six of those $600 computers from CircuitCity will saturate a T1
and pump 3 Mmsgs/day.
So where is the major cost of schemes like hashcash to spammers?
Vernon Schryver vjs(_at_)rhyolite(_dot_)com
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