Thank you to those who answered, I'm learning a great deal about network
time compensation.
On 30/03/13 07:55, David Taylor wrote:
Claudio,
I offer you three monitoring techniques - two programs and MRTG. The
programs are listed here:
Thank you David, I had already spotted your site in another message to
this list/ng, unfortunately I work under linux, so can't use your
programs. But it was really interesting none the less.
On 29/03/13 21:20, John Hasler wrote:
NTP has already used the offset to correct the system clock. You don't
need or want to do anything. When NTP says that the clocks are
synchronized they are as close as it is possible to get them over the
network.
Then why does NTP give a number to the offset and delay?
If the algorithm knows that it's lagging by X s, why doesn't it correct
for that lag?
Alternatively, from my point of view, it ought to say that the clocks
are synchronized to the best of its knowledge without providing delays
and offsets.
On 29/03/13 21:12, Chuck Swiger wrote:
If so why doesn't the offset oscillate?
It usually does, although the most common type of cyclical offset variations
occur with a period of 24 hours, resulting from day/night temperature changes
affecting the quartz crystal.
I may have much faster temperature variations in my case: embedded
boards do vary their core temperature a lot according to their loading.
No air conditioning can solve this, as my embedded boards are inside a
very small case and near batteries and motors (as I said previously I'm
managing a fleet of small robots).
A well-designed compensation system doesn't over-force the corrective adjustment being
made and thus avoids overshooting and then "ringing" back and forth across the
setpoint.
Sure but a well-designed compensation system should also keep lagging or
leading to avoid oscillation.
I'm trying to understand here.
If I send a message through a route, each machine adding their own
timestamp (kernel provided timestamp) at the time of processing, let's
say that between machines 2 and 3 there is a lag of 3.5ms.
Now if I knew that the clock of machine 2 was lagging the time server by
2ms and the clock of machine 3 was leading the time server by 0.5 ms,
why does this not mean that my real lag is 1ms ?
Have all a nice Easter holiday.
Claudio
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