Free Clock Democratizes Atomic Accuracy 178
schliz writes "A new, trial network of software-based clocks could give data centers and networks the accuracy of an atomic clock for free. The so-called RADclock analyses information from multiple computers across the internet by collecting the time from each machine's internal quartz clock, the time it takes for this information to be transmitted across the network, and comparing all the information collected to determine a time that is most likely to be accurate, so machines are calibrated across the network with up to microsecond accuracy — as good as that provided by a $50,000 atomic clock, researchers say."
Re:Use GPS (Score:4, Interesting)
A GPS receiver will be useless as the GPS time currently is (IIRC) 12 seconds ahaed of UTC.
GPS doesn't honor leap seconds. This behaviour is by design as it's quite hard to halt the sattelites orbits for a second.
Re:Nano not micro (Score:2, Interesting)
I don't think it's anything special.
If you want atomic clock accuracy, then you go fetch the time from an actual atomic clock. Even back in the 1980s, I had a Commodore Amiga program that would automagically dial a 1-800 number, fetch the time, and set my internal clock. Doing it today via the web should be a piece of cake.
Re:A new low in editorial savvy (Score:3, Interesting)
- Reduce the potential points of failure from one single bottleneck to infinite peers.
- Require no configuration (some old routers for example have a wrong time and log full of errors because the NTP server preprogrammed is gone).
- Protect against sabotaged NTP servers (in case of attack, or deliberate government intervention).
- Maintain high resolution timers in sync when the internet kill switch is tripped (or any internet-disrupting calamity).
- You're on Mars, and forgot to bring an atomic clock with you on the first colony ship...
- You're just paranoid about anything the government says, even the time...
Also this mechanism adds something new: Accurate time difference between two events (something that can still be very skewed with NTP when you have in inaccurate crystal).
All in all interesting, and worthy of a Slashdot dupe...
Re:Use GPS (Score:3, Interesting)
YRW, it's behind, not ahead.
And that's why you have /usr/share/zoneinfo/right hierarchy anyhow:
Re:A solution in need of a problem? (Score:1, Interesting)
RADclock aims to provide better accuracy than NTP.
TFA
Accuracy on the scale of 50 microseconds has been achieved for distances within 900 kilometres, and accuracy on the scale of 80 to 100 microseconds has been achieved within about 3,500 kilometres - the distance from Melbourne to Perth.
Wikipedia about NTP
NTPv4 can usually maintain time to within 10 milliseconds (1/100 s) over the public Internet, and can achieve accuracies of 200 microseconds (1/5000 s) or better in local area networks under ideal conditions.
Re:Favorite Quote (Score:2, Interesting)
Re:A solution in need of a problem? (Score:3, Interesting)
To answer your implication about time variation between nodes, even a basic ntp server to which your local network nodes sync will keep them in at the same wall clock time, even more so if you follow the protocol and use multiple servers, even if the time source is the servers' quartz clocks. If you have more than a few milliseconds skew after that, you've installed NTP wrong.
If you need more than fractional second timing for syncing a process or physical events, you don't try to coordinate timing over a communications medium without guaranteed latency (like ethernet). This can be seen in certain types of linux superclusters that abandon ethernet and its descendents in favor of synchronous communications.
It's great that these guys are developing a better way to estimate the correct time. I value this sort of thinking, if nothing else.
This sort of breakthrough deserves a web site announcement, or a scientific paper.
If I have to sort through the BS, sponsored articles, and overblown hype to find the useful info on Slashdot, why not skip the middleman and just browse the web itself?
Re:Computer Clock resolution? (Score:5, Interesting)
if a computer's clock only has microsecond resolution, then it stands to reason that you can only synch the computer to within 1 microsecond of accuracy, no?
No. You can sync up to fractions of a clock cycle fairly easily. On average you can only report the time at any instant with around 0.5 uS accuracy, but you can set the edge where it cuts over from one uS to the next as accurately as you want, given enough time to sync...
Slashdot car analogy is I change my oil 4 times a year, so you're saying I can't tell you when I change my oil with any accuracy higher than a whopping 3 months. Yet I assure you, if sufficiently motivated, I can "sync up" such that I change the oil precisely at midnight on the 1st of every third month, with a reportable accuracy of like an hour or so.
Re:Use GPS (Score:2, Interesting)
So it's good enough for relative time or within a system that agreed to use GPS time instead of UTC. Any other setup would require constant manual intervention.
Easy way round this if you can access ntp but need the accuracy of gps:
Assume ntp is accuracte to within 0.5s (oviously it's much more accurate). Take the difference between ntp and gps times and round to nearest second. This gives you the current number of leap seconds, and you can then adjust your gps time with no manual intervention.
Re:A new low in editorial savvy (Score:3, Interesting)
the trick is within a given site it does not matter ~95% of the time if there is a time skew if The Whole Site is wrong by the same amount. So if the error is exactly 5 minutes 14.507693 seconds and the whole site has that same error then everything works out.
In the other ~5% of the time having a few systems sync to say our friends tick|tock.unso.nay.mil (or another NTP server) sorts things out nicely.
Re:Computer Clock resolution? (Score:3, Interesting)
These guys aren't using the PC clock crystal, and they're improving on NTP by a large margin.
Plus they split interval and wall-clock timers for people who really care that their interval measurements don't get screwed with by leap second (or DST) resets and such, and the accuracy of those measurements is down in the ns range.
Re:A solution in need of a problem? PTP (Score:1, Interesting)
Open Source does not mean Free to use.
From the ptpd.sf.net README
- Legal notice -
PTPd was written by using only information contained within 'IEEE Std
1588-2008'. IEEE 1588 may contain patented technology, the use of which is not
under the control of the authors of PTPd. Users of IEEE 1588 may need to obtain
a license for the patented technology in the protocol. Contact the IEEE for
licensing information.