Björn,
On 12/28/2012 12:31 AM, [email protected] wrote:
Magnus,
Doing ~200 us for a non-trival network with real data on it sound about
right.
What kills many assumptions is that the noise-forms fail most of the
normal assumptions about "noise". It's not zero mean, it does not have a
static mean, it does not have a static variance, it is not symmetric, it
is not independent of other traffic, it is not "just another service".
Cheers,
Magnus
But NTP is very much aware of the measurements coming from a complicated
statistical source. Look for 'wedge scattergram'.
http://www.eecis.udel.edu/~mills/database/brief/algor/algor.pdf
http://www.eecis.udel.edu/~mills/database/brief/distlec/distlec.ppt
I am fully aware of it.
NTP has many treatments to the measurements to combat these issues, but
it can't cut down the noise all the way down as you would like to do 1
us or so over large scale networks.
My comment above was to point out that you do need to look hard at the
topic to grasp all the details of it. There are many subtleties and the
wedge scattergram is one of several methods to approach it.
NTP only come that far, given some of the design constraints it has. It
does a good job within those limits.
Cheers,
Magnus
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