Re: GPS Sync Outage

[bert hubert <bert () hubertnet nl>]

Hello everyone,

This email got stuck in the moderator queue for 6 days, I don't know why. I
am pretty sure I subscribed from the right email address.

But, by now this email has been overtaken by events. The more likely source
of the outage now appears to have been the GLONASS year rollover number. 

GLONASS internally operates on four-year plans, and 2020 starts a fresh one.
Some devices may never have seen such a rollover back to day 1. Day 1? Yes,
GLONASS counts from 1.

Forrest Christian did most of the research.

Some fun details can be found in this thread:

https://twitter.com/PowerDNS_Bert/status/1213038807412547584

Also possibly related:

https://twitter.com/sokane1/status/1213928717933662208 on GoPro drones
losing it after the GLONASS rollover.

        Bert

On Wed, Jan 01, 2020 at 02:52:02AM +0100, bert hubert wrote:
> Greetings,
>
> This email is a response to https://mailman.nanog.org/pipermail/nanog/2020-January/105058.html
> in which Forrest discussed GPS time sync issues today.
>
> The galmon.eu project also monitors GPS, and one thing we found is that at
> 20:39:47 UTC today, which is near 2PM MST, GPS PRN 29 emitted a clock update
> that is pretty weird. 
>
> The 't0c' is the t=0 of the clock correction parameters and it went
> backwards by 16 seconds, and it introduced a 5.9 nanosecond clock jump.
>
> This was recorded by 18 of our stations, mostly in Europe and the US east
> coast: 
>
> Tue, 31 Dec 2019 20:39:47.0000 +0000 src 33 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749  
> Timejump: -5.89898 after -16 seconds, old t0c 15750
> Tue, 31 Dec 2019 20:39:47.0005 +0000 src 13 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.9999 +0000 src 3 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.9997 +0000 src 15 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.9998 +0000 src 101 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.9996 +0000 src 32 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.9996 +0000 src 57 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.9999 +0000 src 37 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.0000 +0000 src 19 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:47.0004 +0000 src 49 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.0000 +0000 src 27 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.0005 +0000 src 56 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.0004 +0000 src 41 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.4453 +0000 src 14 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.0001 +0000 src 141 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.0002 +0000 src 40 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.0003 +0000 src 102 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
> Tue, 31 Dec 2019 20:39:48.0002 +0000 src 58 imptow 247203 GPS 29@0: 247206 frame 1 gpshealth = 0, wn 2086 t0c 15749
>
> This was the previous t0c:
>
> Tue, 31 Dec 2019 20:39:18.0000 +0000 src 27 imptow 247173 GPS 29@0: 247176 frame 1 gpshealth = 0, wn 2086 t0c 15750
>
> And this is the next one:
>
> Tue, 31 Dec 2019 21:59:46.9996 +0000 src 33 imptow 252003 GPS 29@0: 252006 frame 1 gpshealth = 0, wn 2086 t0c 16199  
> Timejump: -0.192813 after 7200 seconds, old t0c 15749
>
> We spend more of our time looking at Galileo, but we have all the GPS data.
> I haven't looked enough at GPS to see if "t0c going backwards" is a common
> thing, but it does not look common.
>
> Perhaps this could be related. If anyone wants a copy of GPS traffic from
> today, let me know.
>
>       Bert