Re: [chrony-dev] Issue with version 1.25 and GPRS/GSM connections

[Ed W <lists@xxxxxxxxxxxxxx>]

On 11/08/2011 16:26, Miroslav Lichvar wrote:
> I think I'm able to reproduce the problem in clknetsim. What happens
> is that skew after the third sample is so high that the NTP test4
> (peer dispersion < 16 seconds) fails even for the minimum delay on
> your network and the source is stuck with the three samples. In the
> simulations I see skews over 100 (not ppm!), so the roundtrip time
> would have to be at most ~15 ms to pass the dispersion test.
> 
> Limiting the skew to some reasonable maximum value should fix this
> problem. A workaround is to not use the iburst flag.

Hi, I haven't hit this problem, but theoretically this would be helpful
to me.  I have a dialup connection over satellite with a normal RTT of
about 1sec, but at 2,400 baud, if a single 1,500 byte packet is ahead of
me, then RTT will become 5s, and obviously even higher if multiple
packets get queued

Another satellite system is "broadband", but again with an RTT of around
the 1sec mark, however, it's a contended system and we sometimes see the
RTTs climb steadily towards the 3-4sec mark (but remain reasonably
steady around that level), and oscillate from about 1sec to 3-4 sec and
back over a 10-30+ sec period

It would be very helpful if chrony could at least not get "stuck" in
such a bad situation.  Obviously accept that performance is extremely
limited in such circumstances...

Cheers

Ed W

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