| Re: [chrony-users] Configuration examples and accuracy |
[ Thread Index |
Date Index
| More chrony.tuxfamily.org/chrony-users Archives
]
- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] Configuration examples and accuracy
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Wed, 26 Jan 2022 10:55:18 +0100
- Authentication-results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlichvar@xxxxxxxxxx
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643190923; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=k69lZGhz1rcNQDYvReF3QsAseSQofskqut4boJvYD50=; b=bwLgjhDgfAzdUJv0vRz1yLJHw75KTGTNh66y1aahfsEIANkwevTPfd1UHqP4BNvyCNnnOl 2ixyqaAi2jTKs7p3fsn7C5GY6vMsPCfa8lxuXrurrMz5LxjL40yRwGTDQ72kpa9Lh4ucnk YwYIDP01/BIAd8gSNKhUBFbjGoXu/rc=
On Tue, Jan 25, 2022 at 11:29:04AM -0500, Charlie Laub wrote:
> Hello Miroslav,
>
> Thank you for creating and publishing this new page. The info is very
> helpful and demonstrates the level of accuracy that can be achieved under a
> variety of configurations. I have a local GPS PPS based (via NTP running on
> an R-Pi) Stratum 1 server. The other machines on my network all run chrony
> and reach tens of microseconds error, which is OK but could be better. I
> need to synchronize them in order to coordinate distributed audio playback,
> for which 1msec is too much error between machines. But synchronicity better
> than 100 usec works OK, with 10 usec being the ultimate goal. I will look at
> your examples to see how I can improve the client performance, however, most
> machines (not the stratum 1 server) are WiFi based so I doubt I can improve
> them much more. My clients use a poll interval of 4 or 5 for the GPS based
> local timeserver. No PTP or hardware timestamping is used.
Getting wireless clients within 10 microseconds is going to be very
difficult. The drivers don't even provide a software TX timestamp.
You could try a shorter polling interval combined with the maxdelay and
burst options. You would need to find the minimum peer delay for each
device at which it can get a good measurement frequently enough to
keep the clock in sync. This assumes the network is not loaded for
longer periods of time.
For example:
server ntp.local minpoll 0 maxpoll 2 burst maxdelay 0.0012 xleave
How do you verify that the clients are in sync? I assume they work as
speakers. Is there a tool which can analyse recorded audio of multiple
speakers and tell you how well they agree with one another?
--
Miroslav Lichvar
--
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "help" in the subject.
Trouble? Email listmaster@xxxxxxxxxxxxxxxxxxxx.