[time-nuts] LTE-Lite module

Bob Camp kb8tq at n1k.org
Mon Oct 20 18:06:17 EDT 2014


The top of my list for “new NTP” would be to bring the 1588 hardware packet time tagging into the NTP code base. There’s a pretty good base of hardware out there that tags. It should help things on a loaded system.


> On Oct 20, 2014, at 3:41 PM, Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:
> --------
> In message <60CC0E0EEEE34928B664249EAC88407F at pc52>, "Tom Van Baak" writes:
>>> http://phk.freebsd.dk/time/20141018.html
>> PHK,
>> This is the best news I've heard in a long time; an overhaul of NTP!
> Indeed :-)
>> Instead of tweaking GPSDO algorithms or tuning parameters and
>> having to wait days to see if it works or not, the idea was to
>> "replay" pre-recorded 1PPS data and pre-recorded oscillator data
>> into the PLL. This means one can test any new design change in a
>> GPSDO in a matter of seconds instead of days.
>> So the question is -- could you do the same for NTP?
> Well, first of all it's not days any longer.  My proto-PLL wrangles
> the clock phase in a matter of seconds and frequency in a few
> minutes.  Some of the (really) old NTP assumptions and metrics no
> longer hold, revisiting them opens up a lot of parameter space.
> Second, I'm already doing such simulations, and the ability to
> do that is part of the design basis of what I'm doing.
> I spent a month of my NTP-time trying to resurrect the "SIM" code in
> ntpd, in order to get some kind of reproducible test-bench going and
> in the end I concluded that 100k lines of code is not the way forward.
> My current plan is to release a brand new client-only NTP daemon
> with a decent PLL and high attack resistance before X-mas and then
> work from there to one or two other programs: NTP-slave server (ie:
> stratum 2..14) and a NTP-master/stratum 1 server.
> All along the way, the intent is to try to pull PTP into this also,
> since there is no material (ie: only protocol) difference between
> a NTP and PTP timekeeping program, and the user shouldn't need to
> notice the difference.
> More as it happens.
> The "mini-blog" entries I've started will happen every so often
> when there is some progress to report or interesting data to
> present.
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
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