Subject: [Ntp] Antw: Re: Antw: Re: Antw: [EXT] Re: New Version Notification for draft‑gruessing‑ntp‑ntpv5‑requirements‑03.txt

From: "Ulrich Windl" <[email-masked]>
Date: Fri, 22 Oct 2021 09:47:30 +0200

>>> Martin Burnicki <martin.burnicki=[email-masked]> schrieb am
21.10.2021 um 15:20 in Nachricht
<[email-masked]>:
> Ulrich Windl wrote:
>>>>> Hal Murray <[email-masked]> schrieb am 21.10.2021 um 11:20 in
>> Nachricht
>> <[email-masked]>:
>> 
>> ...
>>> The root of the problem is smearing.  The current implementation hides it
>>> from
>>> the client software.
>> ...
>> 
>> I wondered: Requiring that smearing servers lower (increase) their startum 
> by one or two?
>> So when mixing sources, the non-smearing servers might win the selection.
> 
> If I remember correctly, the stratum number plays not a big role in the 
> selection algorithm of ntpd. It's more important that different time 
> sources agree on the "same" time.

True. Maybe the "rest of the smear correction" (correction that still has to be done) should be added to the dispersion instead.

> 
> So if there's a smearing server in a clique of non-smearing server, the 
> smearing server should be outvoted as falseticker. If the majority of 
> non-smearing servers have the leap second warning bit set, the client 
> should accept it and handle the leap second as usual.
> 
> On the other hand, if the majority of configured servers do the same 
> smearing, the non-smearing server should be outvoted. And in addition, 
> the the smearing servers (which are the majority) do *not* have the leap 
> second warning bit set, so the client should not accept the leap second 
> warning, but instead follow the smeared time that hides the leap second.
> 
> So the client may either smear its time, or step the time for the leap 
> second, depending ion the majority.
> 
>> An other question: Can a smearing server be confused when getting smeared 
> time from another smearing server?
>> (something like: time is "t", but server smeared it to "t-0.5". The 
> receiving server thinks it has to smear it to "t-0.5-1" eventually.)
> 
> If a secondary server gets smeared time from a primary server, it just 
> follows that time and doesn't even notice the leap second, just like any 
> other client.
> 
> So it doesn't add some other smearing offset, *except* if the secondary 
> has a leap second file that forces it to handle a leap second.

So the assumption is that only stratum-1 servers do leap smearing and higher strati even when seeing a leap announcement do "jump"? Or are they expected to ignore the leap announcement? Or do the smearing servers keep the leap announcement for themselves (not pass it on)?
Thinking about it that would demand that a smearing server always indicates "no leap" (LI==00) to ist clients as it actualy converts the leap event (taking one second) to a "smearing interval" (taking hours).

Regards,
Ulrich