🤣

I run pfsense for my firewall/router and have an NTP server running on it.

I did say *might*! 🤣

Yes, I have the same card as Linus. That will be in the next video in this series.

I agree

@@GaryExplains I suspected this was why you were laying such a solid foundation re: computer time

Have look at Jeff Gerling's video, it's pretty good too: ukposts.info/have/v-deo/rIVhrHlosKSStWw.html

What is the name of LTT’s video?

Glad it was helpful!

Glad you liked it!

Glad it was helpful!

MARK!!!

Thanks!

Glad you enjoyed it!

The round trip delay will still be correct but not the offset, as it depends on the back and forth travel times being equal.

No. GNSS satellites have atomic clocks on board and are considered Stratum 0.

@@GaryExplains The satellite has indeed an atomic clock onboard, but it is Stratum 0 only for the satellite: any device on earth (or in space) reading the time signal cannot determine correct time (at high precision) without knowledge of the orbital parameters, the exact location of the receiver, and atmospheric conditions (temperature, pressure, humidity) along the signal path to the satellite. The parameters cannot be measured in the way you demonstrated on the NTP protocol, as GPS only transmits: it is not possible to measure the transmission delay based on roundtrip times. I assisted in the accurate determination of positions of scientific infrastructure to sub mm accuracy based on GPS signals: such measurements take long data acquisition times (hours) and require post processing of all the data, including atmospheric data in order to reach such level of precision. As such, I would personally not (yet) consider a GPS satellite (a single one) sufficiently accurate to be Stratum 0 time reference. But, I'm not a specialist in this field, and I welcome some inputs from specialist, with references to reliable technical documentation. After all, you may be correct Gary - I just have some doubts.

I listen to BBC WS via XM Satellite radio (I'm in North America). BBC has those time signals at the top of the hour. It one case the time signal was about 20s slow (!) by the time the audio eventually made it through all the buffers and reached my ears. Comically bad. More recently it's more like 8-10s late.

@@JxH Or, one could very easily stream and cast BBC World Service with their smartphone. Now everyone around the world with a smartphone of some description can listen to the premiere world news service. 🇬🇧

Anyone can run a time server and make it publicly accessible(don't do that). Companies run them I know that Apple has a few, I assume Google does as well. You can get a list of public ones at: support.ntp.org/bin/view/Servers/WebHome

I noticed that too. You can get a app that backs up Android apps, so you can install them, even if no longer on GP.

Yes, I have the same card as Linus. But really there is little benefit for a prosumer.

From 1950 until 1 April 2007 it was transmitted from Rugby, Warwickshire. The transmitter's original location meant that the clock was referred to as "the Rugby clock". Following its relocation in 2007 to Cumbria, the UK's National Physical Laboratory (NPL) now formally calls the signal "The Time from NPL".

@@GaryExplains Ah, I didn't know they stopped in 2007. No wonder I was struggling to recall, I was clearly rummaging through some very old memories!

It can and does.

@@pilotavery Actually, phones get there time from the cell network. My phone, anyway, won't let me sync to NTP, though my tablet does.

GPS is every second.

Yep, the famous 1PPS. VLF Radio signals give the explicit absolute digital time code every minute. Ideally they'd give it in advance, and then "3, 2, 1, MARK!:"

@@James_Knott As it pertains to the atomic clocks around the world, that are used to obtain an average... How do each of those atomic clocks keep accurate time, such that they are suitable to be included for contributing to the average time? What is IAT?

@@NoEgg4u IAT is International Atomic Time, as I mentioned above. The cesium clocks they use are extremely precise for frequency. As for determining the actual time, it used to be based on stars, but they are no longer accurate enough. How it's done now is a longer story than suitable for here. Search for From Sundials to Atomic Clocks. It's a free download from NIST.

I am not a doctor.

Yes, but this video isn't about time zones.

@@GaryExplains ...just a trivial comment. I was surprised when I discovered that.

Do you have a link to any testing that shows that this video is misleading?

Well, obviously I have show you the top level view. The actual algorithms are clever than that. Multiple messages are used, averages are taken over longer periods of time, plus there are some things to catch outliers etc.

Meanwhile, in the real world, 7 seconds would be an *extremely* long delay, about 100 times longer than what is already not that great. Still, NTP is not designed for microsecond accuracy.

@@JohnnieHougaardNielsen I realize that , and it seems that NTP is good enough , I just expected a fancier principle of operation .

@@GaryExplains I guess they don't call it a PROTOCOL for nothing !

Yes you are correct. What mainly screws up the time synchronization is network asymmetry (not the same path delay between both directions) and also the variations in travel time of the NTP/PTP packets. PTP provides ways to take into account these problems and generate more accurate results.

It isn't a case of "don't start", I have many videos in this style.