[ntp:questions] SNTP accuracy
david-taylor at blueyonder.co.uk.invalid
Thu Dec 27 09:21:38 UTC 2012
On 24/12/2012 20:17, Ran Shalit wrote:
> I read in http://www.sematech.org/docubase/document/4736aeng.pdf that "SNTP
> provides accuracy typically within 100 ms".
> I would like to ask if this means that on a specific system combining two
> machines connected by ethernet (LAN), it can be any number *changing in
> run-time* within 100 msec or that we will reach more or less a constant
> delay number. This is very important because in case it is a constant
> number, even 98msec delay, we can always delete this delay time (98msec)
> and get a time synchronization around zero. Is that right ?
> Best Regards,
Ran, as has already been suggested, why not use full NTP directly
between the two systems? If you are running Windows, you can get down
to "few milliseconds" offset levels with care. For example, see the PCs
named "Hydra" and below on this page:
Exactly how close depends on which PC and which version of Windows.
UNIX like systems, and Windows-8, can get much closer (see Portable PC
Bergen which is even running over Wi-Fi).
Using a local GPS/PPS source can be even better - even on a low-cost
computer like a Raspberry Pi:
Getting Windows to return a time closer than about 15 milliseconds
requires extra programming.
More information about the questions