Free Clock Democratizes Atomic Accuracy

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."

Comments

A solution in need of a problem?

[iserlohn]

NTP solved this ages ago by distributing atomic clock accuracy through the network.

The only problem this will solve is where it is a private network not connected to public NTP servers (or organizations that do not trust public NTP). In that case, they would most likely be able to afford a atomic clock.

Re:A solution in need of a problem?

[David Chappell]

NTP solved this ages ago by distributing atomic clock accuracy through the network.

The only problem this will solve is where it is a private network not connected to public NTP servers (or organizations that do not trust public NTP). In that case, they would most likely be able to afford a atomic clock.

If one reads the explanation at the beginning of the article literally (as the person who wrote the summary did), the article does seem to say that this system averages the time from the cheap quartz crystal clocks in all of the computers in order to arrive at a highly accurate estimate of the true time of day. This of course is absurd. If all of the clocks start out between one and five minutes fast, they will converge on a time that is about three minutes fast. So much for microsecond accuracy!

The article suggests that NTP did indeed solve this problem. Reading between the lines I gather that these researchers are developing the next generation protocol to replace NTP. This will allow all of the nodes to synchronize more tightly with whatever time source (such as an atomic clock) is used.

Re:A solution in need of a problem?

[marcansoft]

GPS also provides an extremely accurate clock signal all around the world (after all, it comes from an atomic clock onboard the satellites). All you need is a GPS receiver. You can put most decent GPS modules into a "clock mode" where you lock their position on the globe and they optimize the calculations to give you the most accurate time.

Re:A solution in need of a problem?

[phoebe]

The next generation protocol has already been invented too, the Precision Time Protocol (PTP) recorded as IEEE 1588, with open source implementations already available.

Re:A solution in need of a problem?

[Anonymous Coward]

The next generation protocol has already been invented too, the Precision Time Protocol (PTP) recorded as IEEE 1588, with open source implementations already available.

PTP isn't a replacement to NTP: it's trying to solve a different problem. It's not useful on a general company LAN, but rather on a network that controls robotics or measurement devices.

Some limitations of PTP:
  * only one "grandmaster" clock, i.e., no redundancy
  * no WAN connectivity; it's UDP multicast-only, and so not very routable
  * no security/signing of timestamps; NTP has security extensions if you need to be able to trust the time
  * patented by HP/Agilent; NTP is both open and free

http://www.meinberg.de/download/docs/ieee1588/meinberg_ieee1588_conference2005_whitepaper.pdf

PTP was designed for small subnets of systems where measurement instruments and robotic systems are running on. This isn't a general PC/server solution.

Re:A solution in need of a problem?

[Odin's Raven]

NTP solved this ages ago by distributing atomic clock accuracy through the network.

You probably missed the point that the project is based in Australia. NTP doesn't work down there, because the Coriolis effect makes Australian clocks turn the opposite way of clocks in the Northern Hemisphere, just like their toilets swirl the other direction. This creates a problem, since many distros have NTP enabled by default, which causes the system clock to run backwards on Australian computers - really makes a mess of the logs, screensavers activate an hour before the computer is turned on, all sorts of odd things. If you start looking at the RADclock code, you'll find that it's surprisingly simple and elegant - they simply reverse the byte order of the NTP messages, and - voila! - their clocks can now run forwards while remaining synchronized.

This explanation brought to you by a six-pack of Fosters.

Most probable time...

[mrt_2394871]

I can imagine the speaking clock:

"At the third stroke, it will be, most likely, sixish"

It solves one problem

[Schezar]

The Financial Sector.

Also, synchronized robotics, precisely coordinated CNC, and a host of other applications. Primarily, it's where absolute time isn't the concern, but rather where arbitrary time must be consistent between multiple devices (accounting for propagation delays, failures, etc...). Of course, protocols like PTP solve this fairly neatly: this particular product solves a different problem, and probably isn't actually useful.

There are two time issues to consider. One is how close your environment is to true time. The other is how close your individual devices are to one another. Messaging time-critical information between devices is severely complicated when the two devices are not on the same plane time-wise. Atomic clocks and the like solve the first problem. PTP solves the second problem. NTP almost (95%) solves both, but falls short in certain extremely time-critical situations.

Favorite Quote

[B5_geek]

One of my favorite quotes relates to this;

Credit goes to Mark Twain (IIRC).

"When you have a watch/clock you always know what time it is. When you have 2 you are never quite sure."

Re:A new low in editorial savvy

[the_olo]

So, someone's invented ntp_time? That's only been around collecting time from time servers, many of which are atomic clock connected, since about 1985.

...

Seriously, could the editor that greenlighted this have done a google search or something?

Could you have done a google search yourself or something?

Then you might find this:

The RADclock project (formerly known under 'TSCclock') aims to provide a new system for network timing within two years. We are developing replacements for NTP clients and servers based on new principles, in particular the need to distinguish between difference clocks and absolute clocks. The term RADclock, 'Robust Absolute and Difference Clock', stems from this. The RADclock difference clock, for example, can measure RTTs to under a microsecond, even if connectively to the time server is lost for over a week!

Re:Uhmmmm

[whyde]

This reminds me of an old joke about a retired Admiral who is responsible for sounding the morning cannon at the naval base, walking past a watchmaker's shop every morning and setting his pocketwatch to the correct time from a reliable old grandfather clock in the store window.

One day, on the walk in, he happens to see the watchmaker cleaning the store windows and mentions how he finds it amazing that the old grandfather clock keeps such flawless time.

"Oh, that old thing?" says the watchmaker. "It drifts horribly, and I have to reset it almost daily."

The Admiral then asks, "Since I've always noticed that it's reliable, from where do you get the time to set it?"

The watchmaker replied, "I use the report from the morning cannon at the naval base. It's always right on time."

Re:Use GPS

[bickerdyke]

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:Use GPS

[Hognoxious]

If it's off by a known amount, I'd expect you could calculate the real value with some kind of mathematical equation.

Re:Nano not micro

[bunratty]

NTP has been around for decades. Even Windows phones home for the time every so often.

Re:Computer Clock resolution?

[mysidia]

That's right. Also, PC clocks tend to be not that great, in terms of reliability of the frequency, and error such as clock drift.

Hence the general recommendation to use NTP to keep your clock in synch with a good time source; a good time source, being something such as an atomic clock, or a radio-based receiver that provides time from a good source.

A PC clock can easily have errors of 100 PPM or higher. Or ~10 seconds of drift per day

Factors that seem small such as temperature can effect the frequency of the clock crystal also

Re:Use GPS

[AmigaAvenger]

Might want to doublecheck your facts. GPS knows about the time difference, which isn't 12 seconds either btw, it is 19. The complete time message, which includes the correct amount, is broadcast every 12.5 minutes, so its possible that when you cold boot a gps, it will be off some amount of time before that is received. (12 seconds is common for lots of GPS engines, they have built in correct for the first 7 seconds of correction, but need the updated time message after connection to get the rest of the update)

Re:Computer Clock resolution?

[vlm]

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.