[ntp:questions] NTP absolute accuracy?

David J Taylor david-taylor at blueyonder.not-this-bit.nor-this.co.uk.invalid
Sat Oct 31 18:03:02 UTC 2009


"Unruh" <unruh-spam at physics.ubc.ca> wrote in message 
news:qg_Gm.50009$Db2.46585 at edtnps83...
> "David J Taylor" 
> <david-taylor at blueyonder.not-this-bit.nor-this.co.uk.invalid> writes:
>
>
>>"David J Taylor"
>><david-taylor at blueyonder.not-this-bit.nor-this.co.uk.invalid> wrote in
>>message news:%XQGm.126$Ym4.58 at text.news.virginmedia.com...
>>> "Unruh" <> wrote in message news:34JGm.50898$PH1.36449 at edtnps82...
>>> []
>>>> Note that chrony will give you a factor of 2 or three improvement 
>>>> over
>>>> ntp  in the errors, assuming that the roundtrip is equally split on
>>>> Linux or BSD.
>>>
>>> For those without wide-bandwidth academic connections - those folks on
>>> cable or ADSL - how good is an "equal split round trip" assumption?
>>>
>>> David
>
>>Thanks, David, David and Jan.  A few milliseconds is what I had 
>>expected,
>>so if you are on a consumer line, what implications does that have for
>>unruh's comment?
>
>>Cheers,
>>David
>
> Which comment?

The one I quoted:

"Note that chrony will give you a factor of 2 or three improvement over 
ntp  in the errors, assuming that the roundtrip is equally split on Linux 
or BSD."

On consumer-grade circuits the assumption about equal round trip is 
unlikely to be valid.

I hope that David Lord can make some tests, and I await the results with 
interest.

Cheers,
David 




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