[ntp:questions] ntpd: time reset problem

Terje Mathisen Terje.Mathisen at tmsw.no
Wed Sep 16 07:23:05 UTC 2009

Unruh wrote:
>> I believe the delays are asymmetric in large part due to vastly
>> different data rates from the earth to the ship (high rate) vs from
>> the ship (low rate).
> No idea why that would make it assymetric. Light does not travel at a
> different velocity simply because it is a crowd of other light ( or
> radio waves).

Maybe because there is always some telemetry and/or image data being 
sent from Mars back to Earth, meaning that even with realtime priority, 
the ntp request must wait until the current packet has finished going out?

OTOH, I'm sure a Mars station will have a network stack/card capable of 
timestamping packets as they actually go out, and not (just) when the 
ntpd process put them in the transmit queue!


- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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