HEADSUP: ntp4 to replace xntpd
This is a HEADSUP message to warn all current users that tha following is being done: - disable xntpd build - enable ntp build - removal of old xntpd/xntpdc binaries as they've been renamed - modifications in /etc/defaults/rc.conf to take the new daemon into account. xntpd will be "cvs removed" in one week approx. -- Ollivier ROBERT -=- Eurocontrol EEC/TEC -=- [EMAIL PROTECTED] The Postman hits! The Postman hits! You have new mail. To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
Huh? What about the impact on all ntp.conf files? Or is this seamless? On Thu, 16 Dec 1999, Ollivier Robert wrote: This is a HEADSUP message to warn all current users that tha following is being done: - disable xntpd build - enable ntp build - removal of old xntpd/xntpdc binaries as they've been renamed - modifications in /etc/defaults/rc.conf to take the new daemon into account. xntpd will be "cvs removed" in one week approx. -- Ollivier ROBERT -=- Eurocontrol EEC/TEC -=- [EMAIL PROTECTED] The Postman hits! The Postman hits! You have new mail. To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED], Matthew Jacob writes: Huh? What about the impact on all ntp.conf files? Or is this seamless? I was just about to start to compose an email with some info on this one when you email arrived. /etc/ntp.conf is the same unless you have a refclock. If you have a refclock you need to revisit your setup. About NTPv4 in general I can say that a lot of things have changed under the hood. Between the two of us Dave Mills and I have managed to get the "nanokernel" to act sensibly in the domain inside +/- 1usec which the old one didn't. (See http://gps.freebsd.dk for what kind of performance this can result in, given appropriate hardware). A lot of changes in the "control" code in ntpd has also changed, and as far as I can tell for the better all around. There is support for *very* long poll intervals (18hours I belive a lot cheaper if you sync by dialup) and burst mode which is more suitable for dial-on-demand kind of lines. There is a new API for PPS kind of signals (I'm also partly guilty here, but I must admit that I think the result is far too rococco for my taste). One thing which is new, is the initial synchronization: it can look broken, but it isn't. You will likely see something like this: 1. Ntpd starts 2. Home in on some server, steps the clock to zero offset. in the process we loose sync again. 3. Catch sync again. Very light and slow adaptation of frequency the clock slowly drifts off to +/- 128msec. 4. Clock is steped again and frequency set to slope of the drift from step 3. 5. Business as usual. Depending on your clock step three can take hours to complete, the better your clock the longer it takes. Dave Mills old rule of thumb applies even more than before: Only tweak your ntp.conf right before lunch. That gives it 24hours to settle before you fiddle it again. You can find much more about NTPv4 on www.ntp.org -- Poul-Henning Kamp FreeBSD coreteam member [EMAIL PROTECTED] "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
Between the two of us Dave Mills and I have managed to get the "nanokernel" to act sensibly in the domain inside +/- 1usec which the old one didn't. (See http://gps.freebsd.dk for what kind of performance this can result in, given appropriate hardware). You may not know the answer to this, but it's worth a shot. Wht kind of accuracy can we expect using 'cheap' off-the-shelf GPS receivers? Nate To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED] Matthew Jacob writes: : Huh? What about the impact on all ntp.conf files? Or is this seamless? Except for additional clocks, I've had no problems using old ntp.conf files with the new ntpd. Warner To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED] Nate Williams writes: : You may not know the answer to this, but it's worth a shot. Wht kind of : accuracy can we expect using 'cheap' off-the-shelf GPS receivers? We're getting, with ntp4 on a 3.x kernel, about +- 4uSec with a cheap gps receiver + atomic clock on a i486 class machine. The clock doesn't want to sync more closely than that, likely due to the large jitter in the 8254 timing device, so the atomic clock is a bit of a waste for this part of our application (there are others it is needed for). With a pentium class machine and w/o the atomic clock "backing", I'd say you could easily get into the sub-micro second range. Warner To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
: You may not know the answer to this, but it's worth a shot. Wht kind of : accuracy can we expect using 'cheap' off-the-shelf GPS receivers? We're getting, with ntp4 on a 3.x kernel, about +- 4uSec with a cheap gps receiver + atomic clock on a i486 class machine. I've got the cheap gps receiver (Garmin 12XL), but what do you mean by an 'atomic clock'? Should the GPS receiver's NMEA messages be adequate enough to do the job? However, all I need is ms accuracy, so anything below 500us is good enough for me. The clock doesn't want to sync more closely than that, likely due to the large jitter in the 8254 timing device, so the atomic clock is a bit of a waste for this part of our application (there are others it is needed for). With a pentium class machine and w/o the atomic clock "backing", I'd say you could easily get into the sub-micro second range. I've got a 486, although running the antenna to an outside window might get exciting. :) Nate To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED] Nate Williams writes: : : You may not know the answer to this, but it's worth a shot. Wht kind of : : accuracy can we expect using 'cheap' off-the-shelf GPS receivers? : : We're getting, with ntp4 on a 3.x kernel, about +- 4uSec with a cheap : gps receiver + atomic clock on a i486 class machine. : : I've got the cheap gps receiver (Garmin 12XL), but what do you mean by : an 'atomic clock'? Should the GPS receiver's NMEA messages be adequate : enough to do the job? However, all I need is ms accuracy, so anything : below 500us is good enough for me. We have a cesium clock, which is generally called atomic clock, that we use for various things in our system. If the GPS gives out a PPS signal for the NMEA, then you can likely hit 1mS w/o any problems at all. Don't know a thing about the Garmin 12XL to know for sure about how it operates. Warner To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
: : You may not know the answer to this, but it's worth a shot. Wht kind of : : accuracy can we expect using 'cheap' off-the-shelf GPS receivers? : : We're getting, with ntp4 on a 3.x kernel, about +- 4uSec with a cheap : gps receiver + atomic clock on a i486 class machine. : : I've got the cheap gps receiver (Garmin 12XL), but what do you mean by : an 'atomic clock'? Should the GPS receiver's NMEA messages be adequate : enough to do the job? However, all I need is ms accuracy, so anything : below 500us is good enough for me. We have a cesium clock, which is generally called atomic clock, that we use for various things in our system. If the GPS gives out a PPS signal for the NMEA, then you can likely hit 1mS w/o any problems at all. Cool. I was under the impression that the cheap NMEA signals only gave 2-5sec accuracy given the 2400 baud speed issues. Don't know a thing about the Garmin 12XL to know for sure about how it operates. It just a standard 'cheap' GPS. Nate To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED], Nate Williams writes: Between the two of us Dave Mills and I have managed to get the "nanokernel" to act sensibly in the domain inside +/- 1usec which the old one didn't. (See http://gps.freebsd.dk for what kind of performance this can result in, given appropriate hardware). You may not know the answer to this, but it's worth a shot. Wht kind of accuracy can we expect using 'cheap' off-the-shelf GPS receivers? I think there are several classes of GPS receivers: "What is a PPS signal ?" Typically handheld/boat naviation stuff. The NMEA or other serial timecodes are at best in the 1msec class. "VP Marketing to VP engineering: Everybody else has a PPS signal make sure our product has one too at no extra cost or schedule changes." You don't want to know. As bad as 1msec have been seen, jitter as bad as 200nsec. "Straight PPS" Derived from the internal clock, typically in the "a few usec" class. "Position hold PPS" State of the art 1 band GPS does a stddev of about 35nsec. The Motorola Oncore UT+ is considered the leader of the pack I think, other vendors have similar devices. "Postion hold PPS + OCXO" OEM products doing basically what the HP 58503A does. We're into cesium like (or better!) quality here. I have *not* heard some rumours about carrier phase tracking low cost receivers, and I was *not* told that they can practically uwiggle the S/A when in position hold mode and I was *not* told to expect them on the market in 1H2000 :-) -- Poul-Henning Kamp FreeBSD coreteam member [EMAIL PROTECTED] "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED] Nate Williams writes: : Cool. I was under the impression that the cheap NMEA signals only gave : 2-5sec accuracy given the 2400 baud speed issues. If you have a PPS signal, then you can get fairly close even if the inforation about the PPS signal comes in at 2400 baud. If you have no PPS signal (eg a DTR or DSR that pulses once a second), then you are SOL for anything better than a few seconds. : Don't know a thing about the Garmin 12XL to know for sure about : how it operates. : : It just a standard 'cheap' GPS. My only GPS experience is with Motorola OnCore receivers. Warner To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
: Cool. I was under the impression that the cheap NMEA signals only gave : 2-5sec accuracy given the 2400 baud speed issues. If you have a PPS signal, then you can get fairly close even if the inforation about the PPS signal comes in at 2400 baud. Hmm, how do I find out how good it is? Nate To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED] Nate Williams writes: : : Cool. I was under the impression that the cheap NMEA signals only gave : : 2-5sec accuracy given the 2400 baud speed issues. : : If you have a PPS signal, then you can get fairly close even if the : inforation about the PPS signal comes in at 2400 baud. : : Hmm, how do I find out how good it is? By looking at the docs to see if it supports PPS or not. PPS is Pulse Per Second and is a dedicated signal that pulses (typ 10mS) once per second. For serial devices, this is typically done by one of the extra RS-232 signals, DSR comes to mind. I suppose you could hook a scope up to the unit and see if any of the signals are acting like PPS. Warner To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED], Nate Williams writes: : You may not know the answer to this, but it's worth a shot. Wht kind of : accuracy can we expect using 'cheap' off-the-shelf GPS receivers? We're getting, with ntp4 on a 3.x kernel, about +- 4uSec with a cheap gps receiver + atomic clock on a i486 class machine. I've got the cheap gps receiver (Garmin 12XL), but what do you mean by an 'atomic clock'? Should the GPS receiver's NMEA messages be adequate enough to do the job? However, all I need is ms accuracy, so anything below 500us is good enough for me. If you only have NMEA you will have a hard time. At 1200 baud you get 50 usec jitter just from the rxclock in the uart (16 * 1200), not to mention how exact the NMEA is transmitted in the first place. There is a pretty vanilla NMEA refclock, so the easist way to find out is to try it out next to (in a network sense) a stratum 1 NTP. -- Poul-Henning Kamp FreeBSD coreteam member [EMAIL PROTECTED] "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
Re: HEADSUP: ntp4 to replace xntpd
In message [EMAIL PROTECTED], Nate Williams writes: "What is a PPS signal ?" Typically handheld/boat naviation stuff. The NMEA or other serial timecodes are at best in the 1msec class. Again, for me this is acceptable. It would be nice to have it better than this, but the kernel's of all the OS's I'm using have at best 1ms precision for all of the applications being used (FS timestamps, application program timestamps, etc...). Well, when I say "at best" I mean it. One NMEA boat-navigation unit I had access to over last winter had +/- 400msec performance. As I mentioned to Warner, is there any way to know how good a particular model of a GPS receiver is? measure it. It's not that hard actually, because you can trust the FreeBSD clock to be allright over short time intervals, so you timestamp the events (NEMA / PPS / Whatever) and analyse the pairwise difference between them: for instance: x2.10 x3.14 x4.12 gives you *two* datapoints: +.04 second and -.02 second. Find the stddev of a couple of thousand samples and you have a good number which is correct to within a factor sqrt(two) or so of the real jitter. -- Poul-Henning Kamp FreeBSD coreteam member [EMAIL PROTECTED] "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to [EMAIL PROTECTED] with "unsubscribe freebsd-current" in the body of the message
