[ntp:questions] Re: Fingerprinting hosts by clock skew

Brian Inglis Brian.Inglis at SystematicSW.Invalid
Wed Mar 9 05:51:27 UTC 2005


On Tue, 8 Mar 2005 20:07:02 -0800 in comp.protocols.time.ntp, Michael
Deutschmann <michael at talamasca.ocis.net> wrote:

>On Sat, 5 Mar 2005, David L. Mills wrote:
>> However, the most useful property of the clock frequency is to track
>> systematic changes, which serves as a quite accurate thermometer.
>> [...] we are talking about millidegrees here.
>> 
>> [...] I should add to that proposal using NTP frequency to
>> reveal outdoor temperature if the IT staff would put the computer
>> outside the building in a doghouse on the roof.
>
>Due to the difficulties of calibrating to real world units, I don't think
>this would be practical.  A sensor such as a thermistor can be waterproofed
>and taken through it's range in a water bath.  You can't do that to a
>computer, especially if it's on.
>
>A better use for the phenomena would be a simple hardware mod to make NTP
>systems more stable.  Find the oscillator can on the motherboard, glue a
>50kOhm-nominal thermistor to it, and then run leads from it out of the case
>and then back to pins 1 & 3 of the joystick port.  Then (the tricky bit...)
>alter ntpd to search for a correlation between the "Joystick 1 X axis"
>reading and the frequency correction, and start actively compensating when/if
>the estimated curve firms up sufficently.

Would be easier to attach the case thermal sensor to the clock
generator, wherever that is nowadays. 

-- 
Thanks. Take care, Brian Inglis 	Calgary, Alberta, Canada

Brian.Inglis at CSi.com 	(Brian[dot]Inglis{at}SystematicSW[dot]ab[dot]ca)
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