[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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