[time-nuts] Minor NTP Issue?
Poul-Henning Kamp
phk at phk.freebsd.dk
Mon Nov 1 16:23:53 UTC 2010
In message <B99A0C81C9964AA3B6BD6AE2124B9691 at Inspiron>, "Jason Rabel" writes:
>I seem to recall that the standard package came with 50' or 150'
>of cable, but even that pre-factored delay wouldn't
>equate to ~300-400us would it?
Once you get below 1ms you need to pay attention to everything, including
ethernet switches. For instance many 8 port switches consists of two
five-port chips connected back to back. That means that the packet
delay inside a group is lower than between groups etc.
But 300µS uncalibrated is not unreasonable. What you need to do is
calibrate against the PPS signal from your GPS.
Poul-Henning
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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