[ntp:questions] impact of arp timeouts on ntp

David J Taylor david-taylor at blueyonder.co.uk.invalid
Sun Oct 3 06:53:23 UTC 2010

"nickname" <alexandre.bezroutchko at gmail.com> wrote in message 
news:8088e467-a7ad-4aa0-95be-af738de143e4 at l20g2000yqm.googlegroups.com...
> Hello,
> I wonder whether ARP timeouts have a negative effect on NTP
> performance. By default in Linux ARP entries get expired after 60s,
> and default NTP minpoll value is 64s. To my understanding this will
> mean that RTT experienced by NTP peers residing on the same Ethernet
> segment, is likely to be affected by ARP resolution process, because
> some NTP packets will be send out by the kernel right away (ARP entry
> is cached) and sometimes the kernel will need to do ARP resolution
> first. My guess this should increase jitter seen by NTP peers.
> I would like to know whether this was already considered.
> Unfortunately right now I don't have time to make experiments to
> measure the effect.
> Best regards,
> Alexandre Bezroutchko

.. and should anyone feel like setting the timeout value in Windows Vista, 
Server 2008, or Windows-7, see:



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