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<div dir="ltr">Same here. Latency and the algo work together. Time outs or un-reachable peers are network issues. </div>
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<div dir="ltr">Paging Randy Bush. </div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif"><b>From:</b> NANOG <nanog-bounces+hannigan=gmail.com@nanog.org> on behalf of John Gilmore <gnu@toad.com><br>
<b>Sent:</b> Tuesday, August 8, 2023 17:01<br>
<b>To:</b> Mel Beckman <mel@beckman.org><br>
<b>Cc:</b> nanog@nanog.org <nanog@nanog.org><br>
<b>Subject:</b> Re: NTP Sync Issue Across Tata (Europe)
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<div class="PlainText">> I was also speaking specifically about installing GPS antennas in<br>
> viable places, not using a facility-provided GPS or NTP service.<br>
<br>
Am I confused? Getting the time over a multi-gigabit Internet from a<br>
national time standard agency such as NIST (or your local country's<br>
equivalent) should produce far better accuracy and stability than<br>
relying on locally received GPS signals. GPS uses very weak radio<br>
signals which are regularly spoofed by all sorts of bad actors:<br>
<br>
<a href="https://www.gps.gov/spectrum/jamming/">https://www.gps.gov/spectrum/jamming/</a><br>
<br>
for all sorts of reasons (like misleading drone navigation):<br>
<br>
<a href="https://en.wikipedia.org/wiki/Iran%E2%80%93U.S._RQ-170_incident">https://en.wikipedia.org/wiki/Iran%E2%80%93U.S._RQ-170_incident</a><br>
<br>
Depending on satnav systems creates a large single point of failure for<br>
worldwide civilian infrastructure.<br>
<br>
Jamming GPS with subtly fake time data near big data centers seems like<br>
an easy move that would cause all sorts of distributed algorithms to<br>
start failing in unusual ways. And in a more serious wartime attack,<br>
many or most GPS satellites themselves would be destroyed or disabled.<br>
Yet digital radio modulations like FT8 or DMR rely on tight time<br>
synchronization among different transmitters. So do many modern<br>
cellphone modulations -- not to mention distributed database sync<br>
algorithms. Depending on any of these for emergency communications when<br>
their time comes from GPS, is a recipe for having no communications<br>
during wars or cyber-wars in which GPS satellites are attacked or<br>
jammed. See a longer explanation here:<br>
<br>
<a href="https://www.ardc.net/apply/grants/2020-grants/grant-ntpsec/">https://www.ardc.net/apply/grants/2020-grants/grant-ntpsec/</a><br>
<br>
I suspect that even today, if you rely on civilian GPS time near the US<br>
White House, Pentagon, or other military targets like bases, you will<br>
discover "anomalies" in the local radio GPS data, compared to what you<br>
get from an authenticated time standard over NTP. How reliable is<br>
civilian GPS time in Ukraine these days?<br>
<br>
John<br>
<br>
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