3 ms·

Gah, just when you think you can trust time.nist.gov Suggestions from the community for more reliable alternatives?

by qmr 10mo ago

evanriley 10mo ago
> Gah, just when you think you can trust time.nist.gov You still can... If you're that considered about 5 microseconds: Build your own Stratum 1 time server https://github.com/geerlingguy/time-pi https://github.com/geerlingguy/time-pi or just use ntppool https://www.ntppool.org/en/ https://www.ntppool.org/en/
- eddyg 10mo ago
  Be aware that there are members of the NTP pool with less-than-honorable intentions and you don't get to pick-and-choose. Yes, they all should provide the time, but they also get your IP address. For example: unlike the IPv4 space, the IPv6 space is too big too scan, so a number of "researchers" (if you want to call them that) put v6-capable NTP servers in the NTP pool to gather information about active v6 blocks to scan/target.
  - ticoombs 10mo ago
    Do you have any acticles or references about this? That would be great research (pun intended) to find out
  - edoceo 10mo ago
    Is this one of those extraordinary claims that requires evidence? Or is it generally true that there are homey-pots in many of these services (NTP, mirrors, etc)
- beala 10mo ago
  It sounds like GPS, and thus a GPS-based stratum 1 server, uses these time servers, but they were successfully failed over: > Jeff finished off the email mentioning the US GPS system failed over successfully to the WWV-Ft. Collins campus. So again, for almost everyone, there was zero issue, and the redundancy designed into the system worked like it's supposed to. So failures in these systems are potentially correlated. The author mentions another solution. Apparently he runs his own atomic clock. I didn’t know this was a thing an individual could do. > But even with multiple time sources, some places need more. I have two Rubidium atomic clocks in my studio, including the one inside a fancy GPS Disciplined Oscillator (GPSDO). That's good for holdover. Even if someone were jamming my signal, or my GPS antenna broke, I could keep my time accurate to nanoseconds for a while, and milliseconds for months. That'd be good enough for me.
  - geerlingguy 10mo ago
    The CSACs that I have in a couple devices are 'atomic', and use Rubidium, but they're a bit lower accuracy than Cesium clocks [1] or Hydrogen Masers [2]. There are a few folks on the time-nuts mailing list who own such exotic pieces of hardware, but those are pretty far out of reach for most! [1] https://www.microchip.com/en-us/products/clock-and-timing/components/atomic-clocks/atomic-system-clocks/cesium-time/5071a https://www.microchip.com/en-us/products/clock-and-timing/co... [2] https://www.microchip.com/en-us/products/clock-and-timing/components/atomic-clocks/atomic-system-clocks/mhm-2020-hydrogen-masers https://www.microchip.com/en-us/products/clock-and-timing/co...
  - rcxdude 10mo ago
    Atomic clocks cover a pretty big range of performance nowadays. You can pick up a used but serviceable rubidium frequency reference for a few hundred dollars but the difference between it and the top of the line clocks is almost as big as the difference between a it and a good pendulum clock.
ajkjk 10mo ago
their handling it responsibly seems like more evidence for trusting them, not less?
monster_truck 10mo ago
I'm more concerned about what you think they did to earn your trust in the first place
ianburrell 10mo ago
Most places that need accurate time get it from GPS. That is 10-100 ns. Also, you can use multiple NIST servers. They have ones in Fort Collins, CO and Gaithersburg, MD. Most places shouldn't use NIST directly but Stratum 1 name servers. Finally, NTP isn't accurate enough, 10-100 ms, for microsecond error to matter.
vel0city 10mo ago
Use the other servers as well: https://tf.nist.gov/tf-cgi/servers.cgi https://tf.nist.gov/tf-cgi/servers.cgi For instance, time-a-wwv.nist.gov. One should configure a number of different NTP sources instead of just a single host.
ssl-3 10mo ago
Yes. Use NTP with ≥4 diverse time sources, just as RFC 5905 suggests doing. And use GPS. (If you're reliant upon only one source of a thing, and that thing is important to you in some valuable way, then you're doing it wrong. In other words: Backups, backups, backups.)

Gah, just when you think you can trust time.nist.gov Suggestions from the community for more reliable alternatives?

by qmr 10mo ago

Gah, just when you think you can trust time.nist.gov Suggestions from the community for more reliable alternatives?

> Gah, just when you think you can trust time.nist.gov You still can... If you're that considered about 5 microseconds: Build your own Stratum 1 time server https://github.com/geerlingguy/time-pi https://github.com/geerlingguy/time-pi or just use ntppool https://www.ntppool.org/en/ https://www.ntppool.org/en/

eddyg 10mo ago
Be aware that there are members of the NTP pool with less-than-honorable intentions and you don't get to pick-and-choose. Yes, they all should provide the time, but they also get your IP address. For example: unlike the IPv4 space, the IPv6 space is too big too scan, so a number of "researchers" (if you want to call them that) put v6-capable NTP servers in the NTP pool to gather information about active v6 blocks to scan/target.
- ticoombs 10mo ago
  Do you have any acticles or references about this? That would be great research (pun intended) to find out
- edoceo 10mo ago
  Is this one of those extraordinary claims that requires evidence? Or is it generally true that there are homey-pots in many of these services (NTP, mirrors, etc)
beala 10mo ago
It sounds like GPS, and thus a GPS-based stratum 1 server, uses these time servers, but they were successfully failed over: > Jeff finished off the email mentioning the US GPS system failed over successfully to the WWV-Ft. Collins campus. So again, for almost everyone, there was zero issue, and the redundancy designed into the system worked like it's supposed to. So failures in these systems are potentially correlated. The author mentions another solution. Apparently he runs his own atomic clock. I didn’t know this was a thing an individual could do. > But even with multiple time sources, some places need more. I have two Rubidium atomic clocks in my studio, including the one inside a fancy GPS Disciplined Oscillator (GPSDO). That's good for holdover. Even if someone were jamming my signal, or my GPS antenna broke, I could keep my time accurate to nanoseconds for a while, and milliseconds for months. That'd be good enough for me.
- geerlingguy 10mo ago
  The CSACs that I have in a couple devices are 'atomic', and use Rubidium, but they're a bit lower accuracy than Cesium clocks [1] or Hydrogen Masers [2]. There are a few folks on the time-nuts mailing list who own such exotic pieces of hardware, but those are pretty far out of reach for most! [1] https://www.microchip.com/en-us/products/clock-and-timing/components/atomic-clocks/atomic-system-clocks/cesium-time/5071a https://www.microchip.com/en-us/products/clock-and-timing/co... [2] https://www.microchip.com/en-us/products/clock-and-timing/components/atomic-clocks/atomic-system-clocks/mhm-2020-hydrogen-masers https://www.microchip.com/en-us/products/clock-and-timing/co...
- rcxdude 10mo ago
  Atomic clocks cover a pretty big range of performance nowadays. You can pick up a used but serviceable rubidium frequency reference for a few hundred dollars but the difference between it and the top of the line clocks is almost as big as the difference between a it and a good pendulum clock.

ajkjk 10mo ago

their handling it responsibly seems like more evidence for trusting them, not less?

monster_truck 10mo ago

I'm more concerned about what you think they did to earn your trust in the first place

ianburrell 10mo ago

Most places that need accurate time get it from GPS. That is 10-100 ns. Also, you can use multiple NIST servers. They have ones in Fort Collins, CO and Gaithersburg, MD. Most places shouldn't use NIST directly but Stratum 1 name servers. Finally, NTP isn't accurate enough, 10-100 ms, for microsecond error to matter.

vel0city 10mo ago

Use the other servers as well: https://tf.nist.gov/tf-cgi/servers.cgi https://tf.nist.gov/tf-cgi/servers.cgi For instance, time-a-wwv.nist.gov. One should configure a number of different NTP sources instead of just a single host.

ssl-3 10mo ago

Yes. Use NTP with ≥4 diverse time sources, just as RFC 5905 suggests doing. And use GPS. (If you're reliant upon only one source of a thing, and that thing is important to you in some valuable way, then you're doing it wrong. In other words: Backups, backups, backups.)