[ntp:questions] NTP absolute accuracy?

David Lord snews at lordynet.org
Sat Oct 31 10:24:32 UTC 2009


David J Taylor wrote:
> "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?

2Mbit adsl here seems to give me mostly maximum variation of 5-6ms
and for 50% its at 0.6ms or less. Remote connections to my servers
shows offset mostly following what I see here but with occasional
irregular blips of from 5ms to 200ms and these don't always seem
to correspond to any local variation in load or network traffic.
Heavy downloads at 230kB/s sometimes have no effect but other
times I see latency as monitored by my ISP shoot up from < 20ms
to >> 100ms which I believe is down to congestion or throttling in
BT network.


David




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