[ntp:questions] impact of arp timeouts on ntp

nickname alexandre.bezroutchko at gmail.com
Sat Oct 2 19:20:34 UTC 2010


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
http://www.gremwell.com/




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