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NIST was 5 μs off UTC after last week's power cut

jeffgeerling.com

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Re: NIST was 5 μs off UTC after last week's power cut

#51

Post by semenko »

I 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 providers synchronizing 5G clocks for time-division duplexing [4]? Google/hyperscalers as input to Spanner or other global databases?

Seriously fascinating to me -- who would be a commercial consumer of NIST TOF?

[1] https://groups.google.com/a/list.nist.gov/g/internet-time-se...

[2] https://www.nist.gov/pml/time-and-frequency-division/time-se...

[3] https://www.finra.org/rules-guidance/rulebooks/finra-rules/4...

[4] https://www.ericsson.com/en/blog/2019/8/what-you-need-to-kno...

Re: NIST was 5 μs off UTC after last week's power cut

#52

Post by ssl-3 »

qmr wrote: post #2

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

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.)

Re: NIST was 5 μs off UTC after last week's power cut

#53

Post by dmurray »

semenko wrote: post #51

I 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…

I never saw a need for this in HFT. In my experience, GPS was used instead, but there was never any critical need for microsecond accuracy in live systems. Sub-microsecond latency, yes, but when that mattered it was in order to do something as soon as possible rather than as close as possible to Wall Clock Time X.

Still useful for post-trade analysis; perhaps you can determine that a competitor now has a faster connection than you.

The regulatory requirement you linked (and other typical requirements from regulators) allows a tolerance of one second, so it doesn't call for this kind of technology.

Re: NIST was 5 μs off UTC after last week's power cut

#56

Post by opello »

sgillen wrote: post #20
V__ wrote: post #10

Has anyone here ever needed microsecond precision? Would love to hear about it.

We don't use NTP, but for robotics, stereo camera synchronization we often want the two frames to be within ~10us of eachother. For sensor fusion we then also need a lidar on PTP time to be translated to the same clock domain as cameras, for which we also need We actually disable NTP entirely (run it once per day or at boot) to avoid clocks jumping while recording data.

In your stereo camera example, are these like USB webcams or something like MIPI CSI attached devices?

Re: NIST was 5 μs off UTC after last week's power cut

#57

Post by herpderperator »

throw0101d wrote: post #35
zahlman wrote: post #28

Earlier quoted context omitted.

> Such precision is important for scientific applications, telecommunications, critical infrastructure, and integrity monitoring of positioning systems. But this precision is not achievable with time transfer over the public Internet How do those other applications obtain the precise value they need without encountering the Internet issue?

> How do those other applications obtain the precise value they need without encountering the Internet issue? They do not use the Internet: they use local (GPS) clocks with internal high-precision clocks for carry-over in case GNSS signal is unavailable: * https://www.ntp.org/support/vendorlinks/ * https://www.meinbergglobal.com/english/products/ntp-time-ser... * https://syncworks.com/shop/syncserver-s650-rubidium-09…

If those other applications use their own local GPS clocks, what is the significance of NIST (and the 5μs inaccuracy) in their scenario?

Re: NIST was 5 μs off UTC after last week's power cut

#58

Post by geerlingguy »

beala wrote: post #42
evanriley wrote: post #5

Earlier quoted context omitted.

> 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 or just use ntppool https://www.ntppool.org/en/

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 correlate…

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/co...

[2] https://www.microchip.com/en-us/products/clock-and-timing/co...

Re: NIST was 5 μs off UTC after last week's power cut

#60

Post by blibble »

dmurray wrote: post #53
semenko wrote: post #51

I 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…

I never saw a need for this in HFT. In my experience, GPS was used instead, but there was never any critical need for microsecond accuracy in live systems. Sub-microsecond latency, yes, but when that mattered it was in order to do something as soon as possible rather than as close as possible to Wall Clock Time X. Still useful for post-trade analysis; perhaps you can determine that a competitor now has a faster conne…

> I never saw a need for this in HFT. In my experience, GPS was used instead, but there was never any critical need for microsecond accuracy in live systems.

mifid ii (uk/eu) minimum is 1us granularity

https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=uriserv:...

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