[ntp:questions] Proposed NTP solution for a network

Unruh unruh-spam at physics.ubc.ca
Fri Mar 6 16:31:59 UTC 2009

Uwe Klein <uwe_klein_habertwedt at t-online.de> writes:

>Unruh wrote:

>> These Gbit
>> switches seem to have, or trigger in the ethernet cards, additional and
>> assymetric delays of the order of 100-200usec. (assymentric delays are of
>> course the worst, since they directly affect the errors in ntp). 

>My guess is you see Store-n-Forward <> Passthrough indeterminisms.

>i.e. some packets go via Passthrough others goe via Store-n-Forward through
>the switch dependent on direction, activity on other ports of the switch
>and the weather.

Does not really matter why, it raises havoc with ntp and the ability to get
really good timing via the net. But thanks for the hint. On one system ( a
100Mb system) I get occasional 1 sec delays (occasional meaning >1%) in the
ntp packets.


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