Re: [Ntp] Resending: Thoughts on draft-ietf-ntp-refid-updates

[Martin Burnicki <[e-mail]>]

Ragnar Sundblad wrote:
> 
> I agree with Philip.
> 
> 1.
> I believe a much more relevant time scale to distribute than a leap smeared
> one is UT1, as in:
> <https://www.nist.gov/pml/time-and-frequency-division/time-services/ut1-ntp-time-dissemination>
> Now, I have no idea how much this is used, but I can easily imagine there
> are astrophysicists that appreciate it.

If you use this with a standard NTP client then your system time will be
UT1 instead of UTC.

> There may possibly be other more relevant ones, like TAI.
> 
> So I guess if other time scales than UTC should be allowed, that you should
> be able to flag for all of them.

And the question is: where to put the flag? If you actually need UTC as
a basis for the local time zones then you don't just need a leap second
warning, but also the current UTC/TAI offset.

> 2.
> Regarding leap smear, I personally believe it should be done in the client
> and not in the server.

Hm, I think it depends on the situation. ;-)

> Today, most unix/linux machines smear an extra leap
> second over two seconds.

Hm, I haven't seen any Unix kernel that does so. Do you have an example?

All I've yet seen on Unix-like systems is that the time is simply
stepped back by 1 s to insert a leap second.

However, the Windows port of ntpd does this on Windows, because except
the next Windows Server version (Server 2019) and associated future
Windows 10 versions, there's no leap second support at all in Windows.

> If you want to do it over 20 hours or whatever,
> and if you want to avoid telling your untrusted kernel about it, then fine,
> handle it as you wish. I understand that modifying the time scale in the
> server is an easy way out if you have control also over the servers, I
> still don’t think that is a good solution more than in very special confined
> cases, and I think it will split the NTP world in two for the entirely wrong
> reasons.

It's indeed just a hack, but if you can let the server do the smearing
you don't have to fiddle with the configuration on every single client,
which caused much work, specifically in a huge network with many clients.

See also my reply to Ask.

Martin
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