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

[Martin Burnicki <[e-mail]>]

Ulrich Windl wrote:
>>>> Hal Murray <[e-mail]> schrieb am 21.10.2021 um 11:20 in
> Nachricht
> <[e-mail]>:
> 
> ...
>> 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.

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.


Martin
-- 
Martin Burnicki

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