RE: [chrony-users] chrony not observing maxpoll - bug?

["Charlie Laub" <charleslaub@xxxxxxxxxxxxx>]

Thank you for the ideas. I will look at the logs. Sorry for not responding
but after joining the list and posting I did not receive any replies because
they were going into a netmail spam folder that I only check now and then.

I have found that I can improve the situation by relaxing some of the
various checks on reply packets e.g. maxdelayratio, maxdelaydevratio, etc.
But it seems that because I am using a WiFi connection to the clients, some
packets do not get replies. They are possibly dropped. The WiFi connection
is very good quality, etc. so this seems a little odd, but if I run
serverstats on a regular interval I sometimes see the LastRX times climb to
several/many times the polling interval. This is even with burst enabled. 

I am no longer using the filter and polling at a short interval. Instead I
have "minpoll 0 maxpoll 6 burst" configured for my local server. This seems
better, as filter N seems to wait until it has received N replies, and this
only compounds the problem with dropped packets.

The local server is hardwired, but the majority of its clients in my home
are on WiFi. This is an absolute necessity, so please don't' suggest I move
all clients to hardwired LAN connections. The entire purpose is to
synchronize WiFi clients as best as possible, and of course I understand
that this will be much worse than with clients on the wired LAN.

Another thing I have tried to improve the synchronization of the WiFi
clients is to try and pin down values for the mindelay using ping. I ping my
local server from the clients, and get the round trip min/max values. Then I
can set mindelay and maxdelayratio accordingly. This helps to reject values
that are e.g. 10x large offsets from what is clearly the nominal offset.
These rare larger offsets really impact the RMS offset value and worsen
synchronicity. The only glitch in this approach is that sometimes the ping
times worsen quite a bit, and then I am rejecting too many RXes. But I will
try to find a happy medium that works under all conditions.

Many thanks for the replies from list members as I figure this out.


-----Original Message-----
From: Miroslav Lichvar <mlichvar@xxxxxxxxxx> 
Sent: Monday, February 8, 2021 1:57 AM
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: Re: [chrony-users] chrony not observing maxpoll - bug?

On Sun, Feb 07, 2021 at 03:22:53PM -0500, Charlie Laub wrote:
> The only thing that I might be able to tailor and improve is why and when
chrony drops or invalidates server replies. If anyone has any advice in that
regard I would like to know it. Thanks.

As was suggested, enable the measurements log, or check the chronyc ntpdata
command. Most likely, the test C is failing for packets that were delayed
too much.

--
Miroslav Lichvar


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