41–50 of 128 posts
> “Currently, nobody uses time except for maybe Spanner at Google, CockroachDB or someone doing database things,” Rosenblum said. “We believe that there’s a lot more places, especially as more and more time-critical things came up. We can do time sync, since we figured out how to do that pretty well. And so we asked: is this part of a trend where we’re going to start programming these systems differently? And [resear…
> “Currently, nobody uses time except for maybe Spanner at Google, CockroachDB or someone doing database things,” Rosenblum said. “We believe that there’s a lot more places, especially as more and more time-critical things came up. We can do time sync, since we figured out how to do that pretty well. And so we asked: is this part of a trend where we’re going to start programming these systems differently? And [resear…
Yup. Going back to the principles of distributed systems, I’m really wondering how “NTP but machine learning” can be used to minimize the clock skew to hundreds of nanoseconds with software only. The RTT between two servers can vary a lot — and way past the calculated minimum RTT. The figures (eg $21M) and names dropped (eg Stanford) are an appeal to authority, which does make me curious. I’d love to see some papers,…
Juicero raised $120M.
Why not just synchronize to GPS time? It is pretty straightforward to get hardware timestamp on the 1PPS from the GPS. And then your time is as precise as the GPS clock, which can have a rubidium standard.
> “Currently, nobody uses time except for maybe Spanner at Google, CockroachDB or someone doing database things,” Rosenblum said. “We believe that there’s a lot more places, especially as more and more time-critical things came up. We can do time sync, since we figured out how to do that pretty well. And so we asked: is this part of a trend where we’re going to start programming these systems differently? And [resear…
IEEE 1588 (Precision Time Protocol) has already solved this problem for every use case that matters and offers microsecond precision. https://www.eecis.udel.edu/~mills/ptp.html PTP takes advantage of special Ethernet switches and other devices which can decode or manipulate the time tags in hardware because yes your switches add latency. This just sounds like more horseshit out of SV. I applaud them for convincing so…
> Those people [fintech, etc.] are interested in our stuff, so obviously [that] means that thing [PTP] is not perfect for them. Part of the problem is, you’re trying to measure individual packets that are going through and get times. It means you have some clock there that you’re reading, and when it goes into the switch, and when it comes out, like, what is that clock doing in terms of its varying in frequency, and stuff like that. And then you get one sample and try to make things of it. It sorta pales in comparison to this big data approach we’re looking about.
This seems like a mischaracterization of PTP (802.1AS), which does use multiple samples to syntonize.
[1] https://www.clockwork.io/resource/ [2] https://www.youtube.com/watch?v=Opf9CBwP5R8
IEEE 1588 (Precision Time Protocol) has already solved this problem for every use case that matters and offers microsecond precision. https://www.eecis.udel.edu/~mills/ptp.html PTP takes advantage of special Ethernet switches and other devices which can decode or manipulate the time tags in hardware because yes your switches add latency. This just sounds like more horseshit out of SV. I applaud them for convincing so…
Applications like Spanner work with nanosecond-level time difference between datacenters. PTP works in microseconds and can even go up to a few milliseconds, making it useless for actual time sensitive use cases.
> “Currently, nobody uses time except for maybe Spanner at Google, CockroachDB or someone doing database things,” Rosenblum said. “We believe that there’s a lot more places, especially as more and more time-critical things came up. We can do time sync, since we figured out how to do that pretty well. And so we asked: is this part of a trend where we’re going to start programming these systems differently? And [resear…
Yup. Going back to the principles of distributed systems, I’m really wondering how “NTP but machine learning” can be used to minimize the clock skew to hundreds of nanoseconds with software only. The RTT between two servers can vary a lot — and way past the calculated minimum RTT. The figures (eg $21M) and names dropped (eg Stanford) are an appeal to authority, which does make me curious. I’d love to see some papers,…
IEEE 1588 (Precision Time Protocol) has already solved this problem for every use case that matters and offers microsecond precision. https://www.eecis.udel.edu/~mills/ptp.html PTP takes advantage of special Ethernet switches and other devices which can decode or manipulate the time tags in hardware because yes your switches add latency. This just sounds like more horseshit out of SV. I applaud them for convincing so…
Their website links [1] to a presentation at Stanford [2]. Mendel Rosenblum briefly compares their concept with PTP at about 45:54. He says: > Those people [fintech, etc.] are interested in our stuff, so obviously [that] means that thing [PTP] is not perfect for them. Part of the problem is, you’re trying to measure individual packets that are going through and get times. It means you have some clock there that you’r…
I was actually reading about this recently and learned about the time problem. Some interesting stuff I remember: * On LAN: NTP can get up to 1ms accuracy and on WAN about 10ms accuracy. * People's 'system clocks' use NTP for synchronization but can still be completely off. * When you call DataTime.now() in Javascript it returns the unix timestamp in UTC time. * Since it is UTC it will have the same value anywhere in…
The problem the OP company is trying to solve is quite a bit tougher.
Of course it sounds extremely stupid, which is why there are so many drive-by "NTP solved this already" comments from people who don't deal with millisecond precision at high accuracy requirements, god forbid sub-millisecond.