[ntp:questions] 1Gb/s network issues - was: Re: OT: GPS18x LVC failure
David J Taylor
david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Mon Oct 12 10:00:04 UTC 2009
"Unruh" <unruh-spam at physics.ubc.ca> wrote in message
news:QsBAm.47742$Db2.29202 at edtnps83...
[]
> Actually those Gb ethernet switches seems to have some really bad and
> variable
> latencies. My system, before they installed Gb switches, had a
> consistant
> roundtrip of 140 usec and gave better than 20usec jitter (with 100Mb
> switches). Since those new switches
> were installed things have gone to hell-- variable roundtrips ( 140usec,
> 300usec
> and up to 1 sec roundtrip) and much much worse jitter. NOt sure where
> the problem
> is, but it sure is terrible.
> Doing a plot of roundtrip vs offset it is definitely one way delay.
Most interesting, Bill. Mine is a relatively cheap and cheerful device
from Netgear (GS608):
http://www.netgear.co.uk/ethernet_network_switch_gs605.php
so whether being very simple and unmanaged is likely to mean that it's
performance is better or worse I leave to speculation or measurement!
Thanks Hal for his comments: the test (resulting in 110 - 140 microseconds
jitter) was using the network controllers built into the PCs. The
stratum-1 source had a 2 - 2.5 microseconds jitter.
Cheers,
David
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