|Re: [chrony-users] chrony with only 2 sources|
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On 02/28/2014 04:33 AM, Miroslav Lichvar wrote:
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.
Probably; they indicated they had a problem with an unspecified attack.
They blocked the port with no notification to the subscribers.
MS Name/IP address Stratum Poll Reach LastRx Last sample
#x TTY 0 4 377 10 +360ms[ +360ms]
^x cache01.dns.rionetworks.c 2 6 177 98 +1005us[+1005us]
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
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.
I'm coming to that realization. I was hoping for better results but I
did this on the cheap (an old wifi access point I had laying around and
a $20 serial TTL module off ebay.)
I do have another board with full serial capabilities. What's a good
serial GPS module with PPS, either 5V TTL or RS232?
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