From: Miles Libbey
Sent: Saturday, October 02, 2004 1:10 PM
<...>
As I recall, it was more like $50k, and that assumed that all of our
email -- both inbound and outbound was signed. Hotmail has publically
indicated that it blocks over 3 Billion messages per day, and yahoo
mail handles mail for a similar size user base -- hopefully that gives
an indication of the scale we are talking about.
I think this deserves a bit more explanation, since PK crypto signing and
validation are so CPU intensive. Does the projected additional hardware
cost consist of crypto accelerator hardware? Are your MTA's currently very
far from being CPU-bound so they can accommodate the extra load with minimal
change? If it is not proprietary information, could you give us some idea
of the CPU, memory, disk, communications and network resources of a typical
MTA in on of your arrays?
My concern is that being involved in DSP and embedded systems, I know what a
CPU load the RSA algorithms represent. General purpose CPU's do not handle
them very efficiently. MTA's that are at small or medium-sized sites with
smaller budgets are often close to CPU-bound, so the extra CPU load may be
far more of an issue for them. The fact that Yahoo's MTA's will only need a
negligible amount of extra resources does not necessarily imply that more
typical MTA's will be the same. Have you investigated the performance of DK
at smaller sites with more typical resources?
Sendmail did a much more valid test in July
http://sendmail.net/dk-milter/benchmark/
and determined their DomainKeys implementation would add 8-16% overhead
to MTAs.
Thanks for posting this link. I was looking for it recently. The
conclusion they draw is based on a large average message size. Most spam
are very short messages, and spam is the preponderance of the incoming
stream, so I don't think the conclusion necessarily agrees with the data
they present. For very short messages, the throughput of this fairly
CPU-rich MTA was reduced to approximately half. I suggest this is more like
what typical sites with high spam loads will see.
--
Seth Goodman