Re: [chrony-users] chrony with only 2 sources

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On Thu, Feb 27, 2014 at 02:40:21PM -0800, Yan Seiner wrote:
> My ISP, in their infinite wisdom, has decided to block port 123 as a
> "security measure".  They do offer one time server on their network,
> but I have no access to any other time server.

I'm curious to know if they block the NTP port as a fix to the ntpd
monlist amplification attacks.

> MS Name/IP address         Stratum Poll Reach LastRx Last sample
> ===============================================================================
> #x TTY                           0   4   377    10   +360ms[ +360ms]
> +/- 5337us
> ^x cache01.dns.rionetworks.c     2   6   177    98  +1005us[+1005us]
> +/-   84ms

This shows that the two sources don't overlap (i.e. 360 +/- 5 ms is
outside 1ms +/- 84).

> refclock SHM 0 poll 4 offset 0.0 refid TTY
> server
> Is there anything I can do to weigh one signal more than the other?

You can set the delay and offset options for the refclock so it
overlaps with the other source. Try "offset 0.36 delay 0.1".

However, without PPS, the timing signal from serial GPS is usually
much worse than what is possible with NTP over internet. You can try
adding "noselect" to the refclock and see how stable it when compared
to the NTP source in the chronyc sourcestats output.

Miroslav Lichvar

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