At least now I can provision Cloud Spanner as a managed service, but is this the future of clouds keeping their services at an advantage?
It’s amazing what you can get, if you just ask. It’s the latter part you really want, which is doable with modern hardware accelerated time stamping and a peering NTP system (like chrony).
PTP is often used now in the Telco world as well as for broadcasting applications.
Sarcasm aside, their NTP servers are less than 2 hops from my router. I know that because of excellent tools like ping and trace route.
With a correctly equipped and configured PTP installation locally, you can expect your clocks to be synchronized on the order of a very small number of microseconds with respect to each other, but the relationship between those and the atomic global clock is something else.
If you are using satellite/GPS time sources, then that's another matter. Why then is it relevant to have an NTP hookup at your ISP?
Also, consistency and accuracy are orthogonal to each other. My servers clocks are consistent and fairly accurate in regards to global time.
Most machines will also know it is 8:11.
The question is how much resolution do you need and are your clocks accuratly synced enough for the thing you plan to do.
You are aware that many of the physics experiments that operate at the edge of what is possible use extremely accurate clocks synced over national and sometimes continental borders?
¹ let's ignore the ones that have been configured incorrectly
You can't trust system clocks in a distributed system to ensure ordering. Some reading:
https://codeburst.io/why-shouldnt-you-trust-system-clocks-72...
Fairly certain distributed physics experiments will be using atomic clocks that are not synchronized over the network. And/or they'll use direct satellite or GPS time sources which have predictable latencies.
My understanding of relativity is that this is principally unknowable and we only assume that speed of light is same in every direction by convention (every few years there’s a paper that claims they managed to measure one way sol but later it turns out they actually measured two-way in a roundabout way) so you can’t really know that?
crazy customer needs is what made up most projects I saw or worked with.
PTP has good support in higher-end switches and routers, but it's difficult to secure and make resilient to failures. It was designed for automation and control networks in factories etc. NTP is a better fit for computer networks, but there doesn't seem to be any switches or routers with HW NTP support. If you really need the best accuracy with NTP, you can find old 100Mb/s hubs on ebay and create a separate network.
There's no networking hardware timestamp support for NTP because NTP has nothing to do with hardware timestamps.
PTP can be done without hardware timestamps, but it was designed with hardware support in mind.
I don't know where you got it that NTP does anything even orders of magnitude close to nanoseconds:
> NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions
https://en.m.wikipedia.org/wiki/Network_Time_Protocol
> The Precision Time Protocol (PTP) is a protocol used to synchronize clocks throughout a computer network. On a local area network, it achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems.
https://en.m.wikipedia.org/wiki/Precision_Time_Protocol
Literally neither solution comes anywhere near nanosecond accuracy.
For reference, there are 1,000,000 nanoseconds in a millisecond
Both NTP and PTP don't care (as protocols) where the timestamps are coming from. That's an implementation detail.
> NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions
That was maybe 20-30 years ago, but not today. The wikipedia article needs an update. If you don't hit a routing asymmetry, in my experience it's usually milliseconds over Internet and tens of microseconds in local network if using SW timestamping. Please note that NTP clients by default use long polling intervals to avoid excessive load on public servers on Internet, so they need to be specifically configured for better performance in local networks.
You can find some measurements with HW timestamping here: https://chrony.tuxfamily.org/examples.html
Note that this is for the system clock, which has to be synchronized over PCIe to the hardware clock of the NIC. That adds hundreds of nanoseconds of uncertainty. It doesn't matter if the hardware clock is synchronized by PTP or NTP.
If you care only about the hardware clocks, it's easy to show how accurate is the synchronization by comparing their PPS signals on a scope. NTP between two directly connected NICs, or a with a hub, can get to single-digit nanosecond accuracy. I have seen that in my testing. It's just timestamps, it doesn't matter how they are exchanged.
I in fact think once you offer atomic clock as a service for any public cloud, distributed transactions become a lot easier to implement thereby disrupting Spanner.