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I thought trading system typically relied on GPS based NTP servers in their own network?

Oh and if you want to make your one: http://www.satsignal.eu/ntp/Ra... . While probably not as accurate as a commercial version, it is a tad slight cheaper.

Better still, make a Pi into a Stratum 1 server:

http://www.satsignal.eu/ntp/Ra...

$400? No way!

I was about to Google for exactly that. There is this RaspberryPi based solution too : http://www.satsignal.eu/ntp/Ra...

There is at least one alternative out there

Whoever proposed tlsdate as an alternative to NTP has no idea how either NTP or tlsdate work. What moving to tlsdate is doing is replacing a well-designed clock-synchronisation protocol talking to precise time servers with an opportunistic gimme-whatver-time-you've-got mechanism that returns a one-off estimate of an approximate time on a web server, assuming the server doesn't just set the time field to random bytes as many do. They're totally different things.

If you're really worried about this, run your own stratum 1 clock and serve NTP off that. If you're worried about the cost of a dedicated NTP server, build it yourself using any number of instructions on the Internet, e.g. these ones.

Not only that, but there are loads of other options, the most basic being that you can use your own personal stratum 1 device, and point all your servers to that. Hell, you can even build your own if you're truly paranoid.

IIRC by default the Windows AD infrastructure has member clients/servers using the Domain Controllers as their local source, and then you only need to re-point the DCs to whatever you want (the registry info documentation for NTP was a bit hinkey as late as Win7/Win2k8, so if you go mucking around in there, do it at your own risk). On the Linux/BSD/*nix side, there's a zillion options to beef up security, and they are drop-easy to enforce with any competent orchestration software (puppet, cfengine, chef, whatever). I only remember the Windows side because a previous employer had a distributed BI system that demanded that all component client devices (a mixture of Windows and Linux) must remain within 5 seconds of each other time-wise (else the whole thing threw an error and stopped).

Like sibling said though, most sysadmins don't dork around with NTP once they get a time source running - few will set up a local NTP relay of sorts, fewer still will have those sources use at least three different and vastly disparate sources to check against, and very few will set up a local authoritative stratum 1 box.

Lots of workarounds, and you really only have to set it up right once, with maybe an occasional (as in once-a-year-or-so) review and tuneup of the infrastructure.

Windows uses the Windows Time Service which IIRC is compatible with but NOT ntpd which is why there is a port of ntpd for Windows if you would desire to use it.

The people behind this project tried to get the ntp hackers interested a year or two ago, but since the only thing they have is a possibly improved distributed algorithm, vs real NTP which has been designed to work even in the face of (intentional or accidental) falsetickers, nobody was very interested.

Any NTP wrangler who's the least interested in accurate local clocks will spend an hour and less than $100 to buy a cheap gps (Garmin GPS18(x) LVC) with Pulse Per Second (pps) output, a USB cable and a 9-pin RS232 connector:

Solder these together according to one of several howtos

(I can recommend http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm, it is quite similar to my own rooftop clock which I've connected to a FreeBSD host in my attic.)

and you'll have a clock source which on average will be exact, with a jitter of a microsecond or two.

Terje
(who used to compile and host the windows ntp binaries for a number of years)