Has anyone here ever needed microsecond precision? Would love to hear about it.
When we collected, correlated, and measured all controlling messages in a whole 4G network. Millisecond precision meant guaranteed out of order message flows.
NIST was 5 μs off UTC after last week's power cut
121–130 of 162 posts
Re: NIST was 5 μs off UTC after last week's power cut
#122Earlier quoted context omitted.
Yes, the US government is banning all those democrat windmills that conspired to blow over the NTP server.
It would greatly decrease electricity prices too. God knows how expensive it is to power those gigantic spinning things
I laughed audibly at that!
Re: NIST was 5 μs off UTC after last week's power cut
#123Earlier quoted context omitted.
GPS could be blocked easily, and AFAIK even given corrupted inputs. And HFT could possibly benefit from blocking or corrupting competitors GPS.
Deploying a GPS jammer in civilized territory is a great way to go to prison.
It's not like foreign adversaries care.
Re: NIST was 5 μs off UTC after last week's power cut
#124Earlier quoted context omitted.
GPS could be blocked easily, and AFAIK even given corrupted inputs. And HFT could possibly benefit from blocking or corrupting competitors GPS.
Deploying a GPS jammer in civilized territory is a great way to go to prison.
Would it actually go so far?
Would the police actually try to investigate from where came the jammer? Might the competing firm possibly even finance an investigation themselves privately? And if so, would the police then accept the evidence?
People have done far more evil things for money.
Re: NIST was 5 μs off UTC after last week's power cut
#125Maybe I missed something, but I don't quite understand the video title "NIST's NTP clock was microseconds from disaster". Is there some limit of drift before it's unrecoverable? Can't they just pull the correct time from the other campus if it gets too far off?
Re: NIST was 5 μs off UTC after last week's power cut
#126Nitpick: UTC stands for Coordinated Universal Time. The ordering of the letters was chosen to not match the English or the French names so neither language got preference.
It's also the time in Iceland, conveniently
Re: NIST was 5 μs off UTC after last week's power cut
#127I found the most interesting part of the NIST outage post [1] is NIST's special Time Over Fiber (TOF) program [2] that "provides high-precision time transfer by other service arrangements; some direct fiber-optic links were affected and users will be contacted separately." I've never heard of this! Very cool service, presumably for … quant / HFT / finance firms (maybe for compliance with FINRA Rule 4590 [3])? Telecom…
> Google/hyperscalers as input to Spanner or other global databases?
Think Google might have rolled their own clock sources and corrections.
Ex: Sundial, https://www.usenix.org/conference/osdi20/presentation/li-yul... / https://storage.googleapis.com/gweb-research2023-media/pubto... (pdf)
Re: NIST was 5 μs off UTC after last week's power cut
#128Earlier quoted context omitted.
TIL/remembered GNSS satellites have onboard atomic clocks. Makes a lot of sense, but still pretty cool. Something like this, I guess? https://en.wikipedia.org/wiki/Rubidium_standard
Yes, either Rb, Cs, or H standards depending on which GNSS system you're using. For the most critical applications, you can license a system like Fugro AtomiChron that provides enhanced GNSS timing down to the level of a few nanoseconds. There are a couple of products that do similar things, all based on providing better ephemerides than your receiver can obtain from the satellites themselves. You can get AtomiChron…
> You can get AtomiChron as an optional subscription with the SparkPNT GPSDO, for instance (https://www.sparkfun.com/sparkpnt-gnss-disciplined-oscillato...).
That's one hell of a healthy profit margin there O.o
The SiTime MEMS oscillator is about 100€ for one single chip, the mosaic-T GPS receiver is about 400€. Add 50€ for the rest (particularly the power input section looks complicated) and 50€ for handling, probably 600€ in hardware cost... sold for 2.500€.
The real money I think went into certification and R&D for a low-volume product - even though most of the hard work is done by the two ICs, getting everything orchestrated (including the PCB itself) to perform to that level of accuracy is one hell of a workload.
Re: NIST was 5 μs off UTC after last week's power cut
#129Re: NIST was 5 μs off UTC after last week's power cut
#130Has anyone here ever needed microsecond precision? Would love to hear about it.
Your speakers do so that people's voices match their mouth movements. The speaker clocks need to be in-sync with the cpu clocks and they operate at different frequencies.