[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...

[dmurray]

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.

[blibble]

> 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:...

[dmurray]

It's 1 us granularity, which means you should report your timestamps with six figures after the decimal point.

The required accuracy (Tables 1 and 2 in that document) is 100 us or 1000 us depending on the system.

[blibble]

> The required accuracy (Tables 1 and 2 in that document)

no, Tables 1 and 2 say divergence, not accuracy

accuracy is a mix of both granularity and divergence

regardless, your statement before:

> 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.

is not true

[metaphor]

> accuracy is a mix of both granularity and divergence

I respectfully disagree.

In context, "granularity" is nothing more than a resolution constraint on reported timestamps. Its inclusion adjacent to the specified "divergence from UTC" is a function of market manipulation surveillance objectives as discussed in preamble item (2), and really doesn't have anything to do with accuracy proper.

[broretore]

any time i am certain of something i never capitalize and i do not end my sentences with periods or use any punctuation because i like people to believe i am an omniscient narrator who cannot be interrupted

[throw0101c]

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

1us is nothing special for GPS/NTP/PTP appliances (especially with OCXO/rubidium oscillators):

* https://www.microchip.com/en-us/products/clock-and-timing/sy...

* https://www.meinbergglobal.com/english/productinfo/gps-time-...

[goalieca]

My guess would be scientific experiments where they need to correlate or sequence data over large regions. Things like correlating gravitational waves with radio signals and gamma ray bursts.

[prpl]

those are GPS based too. You typically would have a circuit you trained off off 1PPS and hopefully had a 10 or so satellites in view.

You can get 50ns with this. Of course, you would verify at NIST.

[metaphor]

> ...and hopefully had a 10 or so satellites in view.

I believe you'll need 12 GPS sats in view to gain incremental accuracy improvement over 8.

[YetAnotherNick]

GPS could be blocked easily, and AFAIK even given corrupted inputs. And HFT could possibly benefit from blocking or corrupting competitors GPS.

[johncolanduoni]

Deploying a GPS jammer in civilized territory is a great way to go to prison.

[dotancohen]

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.

[johncolanduoni]

The victim firm would definitely notice, they’d tell the FCC, and their investigators will show up with a device that literally points them to wherever the jammer is. If you do this for stupid, silly reasons you will get fined[1], if you do it in commission of another crime you will probably get made an example of. It doesn’t matter how evil you are, it’s hilariously easy to get caught doing this.

[1]: https://www.nj.com/news/2013/08/man_fined_32000_for_blocking...

[cinntaile]

It's not like foreign adversaries care.

[johncolanduoni]

The parent was saying HFT firms would do this to other HFT firms. They would care about doing this kind of thing - it’s not a white collar crime. And foreign adversaries would care about doing this during peacetime, especially for very unclear benefit.

[bob1029]

> a commercial consumer

Where does it say these are commercial consumers?

https://en.wikipedia.org/wiki/Schriever_Space_Force_Base#Rol...

> Building 400 at Schriever SFB is the main control point for the Global Positioning System (GPS).

[throw0101c]

> I've never heard of this! Very cool service, presumably for … quant / HFT / finance firms (maybe for compliance with FINRA Rule 4590 [3])?

To start with, probably for scientific stuff, à la:

* https://en.wikipedia.org/wiki/White_Rabbit_Project

But fibre-based time is important in case of GNSS time signal loss:

* https://www.gpsworld.com/china-finishing-high-precision-grou...

[esseph]

I'm sure all of that is true, but so is "Department of Defense".

They're also the largest holder of IPv4 space, still. https://bgp.he.net/report/peers#_ipv4addresses

[squigz]

Why does the DoD hold so many IPv4s?

[ErikBjare]

They were assigned a huge prefix at the creation of the internet iirc

[esseph]

ARPANET, precursor to the internet, was a DoD project.

[ignoramous]

> 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)

[mmaunder]

SIGINT as a source clock for others in a network doing super accurate TDOA for example.

[anilakar]

But they do not need absolute time, and internal rubidium clocks can keep the required accuracy for a few days. After that, sync can be transferred with a portable plug, which is completely viable in tactical/operational level EW systems.

[secondcoming]

I think Google uses chrony instead of NTP

[creatonez]

Google doesn't use chrony specifically, just an algorithm that is somewhat chrony-like (but very different in other ways). It's called Google TrueTime.

[secondcoming]

Oh right. Their cloud-init script uninstalls NTP and installs chrony each time our VMs boot

[creatonez]

Ah yeah. For VPS tenants it makes sense they would default to Chrony. They have a public facing pool of NTP servers at `time.google.com`, and for tenant use they provide `metadata.google.internal`, which is probably where the Chrony config file points. IIRC TrueTime is not actually open source and is only used internally on their infrastructure.

[machinationu]

science equipment, distributed radio-telescopes where you need to precisely align data received at different locations