From Newsgroup: comp.protocols.time.ntp

Well,

We could start a discussion what "UNSYNC" really means:
Does it mean the clock is free-running (not updated by the clock discipline), or does it mean the clock's estimated offset is "just terrible" (like 16 seconds)?
With the former definitions it's likely that an issue is discovered earlier by monitoring IMHO.
I think an UNSYNC clock could still provide an estimated an maximum error.

Kind regards,
Ulrich Windl

-----Original Message-----
From: Miroslav Lichvar <mlichvar@redhat.com>
Sent: Wednesday, July 2, 2025 4:55 PM
To: Windl, Ulrich <u.windl@ukr.de>
Cc: Dave Hart <davehart@gmail.com>; questions@lists.ntp.org; Jürgen Perlinger <juergen.perlinger@t-online.de>; Jürgen Perlinger <perlinger@ntp.org>; Windl, Ulrich <windl@ntp.org>
Subject: [EXT] Re: Re: Re: Delay in Switching to Stratum 16 After Local Reference Loss on ntpd 4.2.8p18

On Wed, Jul 02, 2025 at 09:50:37AM +0000, Windl, Ulrich wrote:

Miroslav,

from the RFC citations found in the bug report it seems to be specified

differently, or I misunderstood.

If you are referring to the Figure 24 of RFC 5905, which has "return (UNSYNC)" for this path, there doesn't seem to be anything suggesting
that should be handled by resetting the clock to an unsynchronized
state.

The clock_select() function in A.5.5.1 doesn't have a return value and
in this case when no usable sources are present it doesn't do
anything, it just returns.

/*
* There must be at least NSANE survivors to satisfy the
* correctness assertions. Ordinarily, the Byzantine criteria
* require four survivors, but for the demonstration here, one
* is acceptable.
*/
if (s.n < NSANE)
return;

--
Miroslav Lichvar

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From Newsgroup: comp.protocols.time.ntp

On Fri, Jul 04, 2025 at 06:54:13AM +0000, Windl, Ulrich wrote:

Well,

We could start a discussion what "UNSYNC" really means:
Does it mean the clock is free-running (not updated by the clock discipline), or does it mean the clock's estimated offset is "just terrible" (like 16 seconds)?

I think in the context of the clock_select() function it means there
is no source selected and the clock cannot be updated. The selection
itself doesn't change the status of the clock. If it was previously
considered to be synchronized, it will still be synchronized.

With the former definitions it's likely that an issue is discovered earlier by monitoring IMHO.

The monitoring can check the reachability directly and discover the
issue even sooner, no need to wait for the orphan timeout to activate
after the source becomes unreachable.
--
Miroslav Lichvar

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