Feeding GPS Time to a Private NTP Server? 52
farrellj asks: "I have a customer that wants to be able to sychronise time on hundreds of servers that are spread all across the continental US and Hawaii. He was using publicly accessable NTP servers, but would rather have his own server that is not dependant on outside servers, and not have to worry about NTP based attacks. You can get a good quality and accurate time from GPS, so he looked at using a GPS reciever hooked up to a machine in his server room, but none of the GPS software out there seem to be able to just pull out the time, and then feed it to an NTP server. Has anyone tried to do this before, or know of a program that will read at GPS reciever and feed it to a NTP server process?"
er. (Score:2, Informative)
Trimble's Pathfinder. If you need some code I may be able to dig some up. A warning, it'll be in VB, but it works.
GPSD (Score:5, Informative)
http://russnelson.com/gpsd/
Hows about this? (Score:4, Informative)
NMEA (Score:3, Informative)
Buy a Serial Data GPSAnd Grep the detail from the output.
Little Program can easily be found on google (search NMEA GPS).
List of Progs [vancouver-webpages.com]
Here is a simple one [vancouver-webpages.com]
Two Standard Exist for the GPS Output NMEA. Most can provide this information via RS232
Less Than 20 Char to read from the Port. Automatically received once per second. Parse the data with PERL/AWK/SED/JAVA/C it's very simple.
Re: NMEA Doesn't work (Score:2)
Use the standard Unix NTP dæmon: nptd ... (Score:5, Informative)
Ntpd supports many GPS reference clocks [udel.edu] directly, so you don't need any special software to "pull out the time, and then feed it to an NTP server".
Re:Use the standard Unix NTP dæmon: nptd ... (Score:1)
Re:Use the standard Unix NTP dæmon: nptd ... (Score:2)
he points out ntpd already supports GPS reference clocks, that nothing special is required bar buying the right hardware.
sheesh...
Re:Use the standard Unix NTP dæmon: nptd ... (Score:1)
Try using clockspeed instead (Score:1)
Look at clockspeed [cr.yp.to] as an alternative to other NTP clients. It's a package of programs that allow a computer to calculate any skew in its own clock, so it doesn't have to constantly query an NTP server for the accurate time.
You may find that you won't need an in-house NTP server after all.
www.ntp.org (Score:4, Informative)
gps+ntp in a box (Score:3, Informative)
they have boxes that sync off of either gps or cdma (for those places where you can't get a good view of the sky). the gps model with the stock oscillator can go several hours without satellites before it drifts too far and only needs a single satellite rather than a full multi-sat lock to sync its clock. upgraded oscillators are available for better and longer term stability. we use the gps version at our observatory to provide ~1 ms time over the network via ntp and ~10 us or better time via the PPS and kPPS outputs. we looked into hooking external gps receivers to PCs running ntpd via serial and PPS, but these praecis boxes are a much easier to configure and maintain solution to the problem and likely more robust as well.
tim
You need TARDIS (Score:4, Interesting)
--Mike--
Re:You need TARDIS (Score:1)
Moderators, please pass this post by. I'm just having a little fun before I take my medication. No harm, no foul.
Re:You need TARDIS (Score:1, Funny)
Why don't people use the resources at hand? (Score:3, Insightful)
How to find the answer to the question the user has posed:
This has to be the lamest question in the history of "Ask Slashdot".
<Whine>
</Whine>
Quit whining. (Score:2)
Re:Why don't people use the resources at hand? (Score:1)
Here's a suggestion. Why doesn't the "Ask Slashdot" section become a more free-for-all message board, separate from the rest of slashdot so that anyone can ask whatever stupid question they feel the need to ask?
The questions they ask could also be user-moderated, then the best ones could show up on the front page from time to time.
That's K5 (Score:2)
Re:That's K5 (Score:1)
whatever, who cares
Linux-Mag + ArcTime = Cross Platform Creaminess (Score:1)
Check out this article.
http://www.linux-mag.com/2000-12/guru_0
Here they tell you where to buy an Atomic Time PC Deskclock with serial interface. $99.00 plus s+h.
http://www.arctime.com/
The article provides an expect script to read the data from the clock. This is cool for UNIX servers. For Windows servers, use perl with the expect module to retrieve the time, then use the "Time" command to set the time.
Cross platform creaminess at a fraction of the cost!
You could also cheese out and use the windows software that comes with the clock, if you are a slacker.
Why not use what broadcasters use? (Score:1)
Check out (Score:1)
Also check out NIST's [nist.gov] list of Manufacturers of Time and Frequency Receivers [nist.gov].
Did you check the NTP FAQ? (Score:2)
Here's a good link [udel.edu] that has information on syncing your private NTP server to GPS.
NTP based attacks? (Score:2, Insightful)
Just use NTP and be done with it. Besides, it's much easier to implement. Hell, use one server as the public NTP client, and then have the rest of your servers poll the previous machine. You could do that a couple of times considering the machines that are all over the US...
I still don't understand the question - at least what the issue *really* is. Besides, wouldn't the GPS solution cost a bit more?
Phil
Re:NTP based attacks? (Score:2)
Re:NTP based attacks? (Score:1)
Phil
Re:NTP based attacks? (Score:2)
An attacker doesn't have to worry about each individual attack succeeding. The IIS worms, for example, seemed to work quite well even though most of their packets didn't reach a vulnerable server. I hope that the built-in NTP clients on XP and MacOSX have been thoroughly audited...
Re:NTP based attacks? (Score:1)
The likelyhood that someone would be doing a port scan that was searching an open port at the exact time that NTP polled its server is extremely unlikely. Even so, then this still isn't any worse off than any other client software that opens a port - http requests for instance...
Besides, the beauty of stateful firewalling and reverse-lookups would prevent your case from happening...
Phil
Re:NTP based attacks? (Score:2)
phk (Score:3, Interesting)
Re:phk (Score:2)
Even better (Score:2)
They have a 1U hardware unit that does a 6-channel GPS time sync, and has all kinds of crazy outputs for your ntp machine (IRIG-B, pps, ppm, etc). But better yet, you could just plug an ethernet jack into their box and it has an ntp serevr built in. Ideally you'd make this your tier-1, and put a couple of unix NTP boxen in the second tier to serve to other machines - you don't want tons of clients hitting the ntp port on the little hardware box.
As a meta note - this is one of many similar peices of hardware available out there from many companies. It took one google search for "GPS NTP hardware", and this was like the fourth link on the page. This is not ask slashdot material, it's just a dumb question from someone who can't use a search engine.
Re: (Score:2)
Re:good luck getting a signal (Score:1)
Good Point. Another post provided a link to http://www.endruntechnologies.com [endruntechnologies.com] they have a 1U rackmount system that gets it time from CDMA cellular network instead of GPA.
You have a better chance of getting CDMA signals in building than GPS. Plus, since you don't need the positioning aspects it seems like overkill to use GPS. ;-)
BalamIf you know which end of a soldering iron to use.. (Score:1)
Of course, if you only need per-second precision, and you really want to go cheap, get a handheld GPS off the pegboard at Wal-Mart and use one of the software packages mentioned elsewhere, but don't expect the same level of precision as the dedicated units mentioned.
How lame.... (Score:3, Insightful)
(Modded down as irrelevant/troll/slam on the editors)
GPS vs WWV (Score:3, Insightful)
A much better solution is to use a standard shortwave receiver that can pick up the digital time signal from WWV. That signal is much stronger and can probably be picked up inside most buildings (perhaps with a simple antenna) in most of the country. That's why this is the signal used by desktop "atomic clocks." You might be able to use one of them as a time source, but I would suggest checking the NTP documentation for recommendations for hardware that supports PPS signals. There's also some websites describing DIY radio receiver hardware.
The downside of this approach is that there's a propogation delay in the ground signal. GPS should give you the current time accurate to microseconds, while the radio delay may be in the milliseconds. (Ground waves are closer to a signal down a wire than a signal through free space, so the prop speed is well under 'c'.) This should not be an issue except for the most demanding uses.
Curiously enough (Score:2)
I'm using Compass from gpspilot.com [gpspilot.com] to view the NavMan's data. The Lat/Lon are reported correctly, as is the altitude. As such, the heading and speed calculations also come out correct. What's really odd to me is that it works at all if it doesn't know the correct time -- I thought that's the whole idea behind GPS.
Please don't try to blame my watch for the problem -- I live and work in Boulder and set my watch to the definition of Correct Time.
For a good time, call 303-499-7111.
Appliance (Score:4, Insightful)
These are rack-mountable 1u servers designed for service provider environments. I have deployed several such systems.
Have a look at TrueTime" [truetime.com] for an example.
Some of these systems are Linux/ntpd/gpsd based, but come with support and in a turn-key format with Web based GUI.
HP/Agilent make a couple GPS time synchronizers (Score:1)
From the pictures, a couple of them look to be rack-mountable.
Introduction to GPS timing solutions [agilent.com]
GPS Indoors? (Score:2)
My time-sync... (Score:1)
1 0 * * *
1 12 * * *
It keeps my server sync-ed to no more than 0.8 seconds of drift at any given time.