Re: [ntp:questions] ntpdate.c unsafe buffer write
Maarten, The natural behavior of a bunch of oscillators near the same frequency is to become one giant phase-locked oscillator. Adding a bit of random fuzz at each poll turns each oscillator into a mini random-walk which breaks up that tendency. The fuzz is not a lot, like 10 percent. Dave Maarten Wiltink wrote: > "David L. Mills" <[EMAIL PROTECTED]> wrote in message > news:[EMAIL PROTECTED] > > No, there is no random delay at startup. Each association starts one second after the previous one. The random backoff occurs only after a step. >>> >>>Is there also a random backoff after an increase of the polling >>>interval? > > >>No. However, there is a small dither of a few percent at all poll >>intervals to resist self-synchronization. > > > Wouldn't that be a nice feature to add? If it's currently polling a > server on, say second 100 (reckoned externally) of 256, to go to > either 100 _or 356_ of 512. > > I understand that there are already some random waits in the client > code and Internet servers are well protected by random noise. But > for large numbers of clients in a uniform environment that were all > started at about the same time, is there any way they tend to > naturally disperse across the final 1024s polling interval? > > Groetjes, > Maarten Wiltink > > ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Geographical diversity of Stratum 1 servers
> The GPS computation of location, elevation, and time involves a system > of four simultaneous equations which can be solved for time, lattitude, > longitude, and elevation. Doing an extended "site survey" can refine > your location and elevation. The better location data, the better the > solution for time. The Tymserve (assuming model 2100 since that was the last and most popular) does a site-survey on power-up. Unfortunately you can't manually input your location (if you know it is more accurate) but the TS2100 does a pretty good job. It also disciplines an oscillator from the 1PPS so that it can flywheel in holdover mode. Jason ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Geographical diversity of Stratum 1 servers
Are both your current clocks using the same GPS antenna? If so, there is a common point of failure right there. If you put a 3rd clock w/3rd antenna at a different location you can do some interesting measurements between the 3. GPS is going to give you the most accurate / stable time (assuming you don't have interference). WWVB & LORAN-C are alternatives to GPS... But unless your location prevents the use of GPS is would still be the preferred time source. If you ever want to get rid of the Tymserve, I'll take it! :) > Looking for a reference on geographical diversity of Stratum 1 servers (GPS > appliances, in this case). We have two clocks now (an old Datum TymServ > with a Symetricom sticker) and another unknown brand. We'd like to add a > third at a completely different facility a mile or more away. > > What, other than the business continuity angle can I use? I'm assuming it > would be better to have the clocks separated from a GPS perspective, too. ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Starting ISC NTP -4.2.4
I've compiled some RPMs for RHEL/CentOS that are using the latest stable version of NTP... Or you can build your own from the SRC RPM... http://ntp.extremeoverclocking.com/rpm/ Jason > Hi All > > Iam trying to install ISC NTP-4.2.4 on RHEL 4. But Im not able to start > the services. > > I firstly removed the default rpm and then compiled the latest version, > configured the ntp.conf file, but Iam not able to start the service. I > give the command /etc/init.d/ntpd start. # prompt comes back. > > Can anyone guide me in figuring out and solving the problem > > Regards > Vivek Aggarwal ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] no ntp synchronisation: 2s to 6s time shift !
Unruh wrote: > Any place where these different clock models is described? Hm, I think "clock models" in the sense of NTP is not correct in this context. AFAIK there is only one "clock model" in the Linux kernel which uses one of those "clocksource" modules as its base for timekeeping, similar to the way ntpd uses a refclock as time source. Each of the clocksource modules deals with a dedicated timer or counter which may or may not be available on a specific hardware architecture, i.e. the x86_64 hardware may provide different timers in its chipset than the i386 architecture. > And defined (what is tsc?) The only place I've found to get an overview is the file Documentation/kernel-parameters.txt which is part of the Linux kernel sources. This also lists which clocksource modules may be available for which hardware architecture. Here's the relevant part from a 2.6.22 kernel: clocksource= [GENERIC_TIME] Override the default clocksource Format: Override the default clocksource and use the clocksource with the name specified. Some clocksource names to choose from, depending on the platform: [all] jiffies (this is the base, fallback clocksource) [ACPI] acpi_pm [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, pxa_timer,timer3,32k_counter,timer0_1 [AVR32] avr32 [IA-32] pit,hpet,tsc,vmi-timer; scx200_hrt on Geode; cyclone on IBM x440 [MIPS] MIPS [PARISC] cr16 [S390] tod [SH] SuperH [SPARC64] tick [X86-64] hpet,tsc As already mentioned by David Woolley the TSC counter is a register inside Pentium CPUs or higher. The tick rate corresponds to the CPU clock, so if the CPU clock changes due to power saving efforts this has to be taken into account when measuring time intervals. The acpi_pm module uses the ACPI Power Management timer which is available on every PC which supports ACPI services. The hpet module uses the High Precision Event Timers indroduced by recent Intel chip sets. AFAIK it's a replacement for the old Periodic Interrupt Timer from the original IBM PC architecture which used to generate periodic interrupts at 18.2 Hz under DOS. I don't know the exact details or advantages/disadvantages of those timers. However, from several postings here in the NG and elsewhere I've seen that certain modules may not work properly on certain chipsets. This must not necessarily be due to the modules, AFAIK there are also chipsets out there where the timers don't work properly and would require specific workarounds. Martin -- Martin Burnicki Meinberg Funkuhren Bad Pyrmont Germany ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Starting ISC NTP -4.2.4
On 2008-02-13, Aggarwal Vivek-Q4997C <[EMAIL PROTECTED]> wrote: > Iam trying to install ISC NTP-4.2.4 on RHEL 4. But Im not able to start > the services. There is no such thing as ISC NTP. You are probably using the NTP Reference Implementation from www.ntp.org. > I firstly removed the default rpm and then compiled the latest version, > configured the ntp.conf file, but Iam not able to start the service. I > give the command /etc/init.d/ntpd start. # prompt comes back. ntpd is a daemon. So it does not produce output on the console. You have to look in your syslog for ntpd related messages or your ntp log (if you have that configured). Use 'ntpq -p' to see the peerstatus billboard for your ntpd. The current Distribution Documentation is linked from http://www.ntp.org/documentatation.html and http://support.ntp.org/doc Community Supported Documentation is available at http://support.ntp.org/support -- Steve Kostecke <[EMAIL PROTECTED]> NTP Public Services Project - http://support.ntp.org/ ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Is there a document that describes the recommandation for configuring ntp ?
Thierry MARTIN wrote: > Hi all, > > Many of you kindly answered my previous questions, thanks a lot for that. > > Now I realise that I got a lot of "tips", that might be included in a > "recommandations" doc. > > So my quesiton becomes: > > Is there a document that describes the recommandation for configuring ntp? > > I mean -for instance-, it seems that "everybody" here knows that a > configuration with only two ntp sources should be avoided; so is there a > doc where I can find this kind of information? > Yes, there is! http://www.ntp.org/ and follow the links you find there. ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Geographical diversity of Stratum 1 servers
Peter Laws wrote: > Looking for a reference on geographical diversity of Stratum 1 servers > (GPS appliances, in this case). We have two clocks now (an old Datum > TymServ with a Symetricom sticker) and another unknown brand. We'd like > to add a third at a completely different facility a mile or more away. > > What, other than the business continuity angle can I use? I'm assuming > it would be better to have the clocks separated from a GPS perspective, > too. > > Cites? AFAIK geographical diversity does nothing to improve the time. It does add some robustness. If you are powered from different substations, good. Are the sites far enough apart to avoid being caught in the same flood, fire, earthquake, explosion, chemical/biological/radiologcal contamination, etc? There is something called "differential GPS" which can help refine position data; e.g. if you have GPS at both a known and an unknown location, the difference between readings can be used to refine the unknown position. The GPS computation of location, elevation, and time involves a system of four simultaneous equations which can be solved for time, lattitude, longitude, and elevation. Doing an extended "site survey" can refine your location and elevation. The better location data, the better the solution for time. ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Is there a document that describes the recommandation for configuring ntp ?
This looks like what I was looking for. Thank you. Martin Burnicki a écrit : > Hi Thierry, > > Thierry MARTIN wrote: >> Hi all, >> >> Many of you kindly answered my previous questions, thanks a lot for that. >> >> Now I realise that I got a lot of "tips", that might be included in a >> "recommandations" doc. >> >> So my quesiton becomes: >> >> Is there a document that describes the recommandation for configuring ntp? > > The best place to look is the NTP support wiki at > http://support.ntp.org/bin/view/Support/ > which covers many aspects of NTP configuration. > >> I mean -for instance-, it seems that "everybody" here knows that a >> configuration with only two ntp sources should be avoided; so is there a >> doc where I can find this kind of information? > > This particular topic is covered at > http://support.ntp.org/bin/view/Support/SelectingOffsiteNTPServers#Section_5.3.3. > > That section also teaches why even 3 time sources may not be appropriate, > and using at least 4 is a better choice. > > Martin ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] NTP and ADAM
noosh wrote: > Martin Burnicki wrote: >> Neither the GPS nor the ADAM are NTP servers, so why should a client find >> it? > if i do the following > GPS---> PC(NTP) > Serial Port > > the time is synchronized by GPS. Right. However the PC is your NTP server and the GPS device is just a reference clock which is read by the GPS program running on the PC. >> What might be possible is to configure the local NTP daemon to read the >> "serial" ref clock via the converter's emulated port. > > What do u mean by that? how can i do that? can you give more detail of > your idea? In the figure above the GPS devices provides a serial port which is connected to one of the PC's serial ports. The NTP program on the PC opens that serial port and uses a special driver (e.g. the parse driver or the NMEA driver) to read the time from the GPS clock, depending of the string format send by the clock. >From your initial post: > this is my first time that i have to work with ADAM 4577. it is 1 port > universial serial gateway.now it is like this > > GPS ->ADAM 4577 ->PC1 > serial Port LAN > > unfortunatelly PC cann't find ADAM as its NTP Server. has anyone work > with this ADAM 4577? So ADAM is a serial-to-LAN converter which reads the serial output of the GPS receiver and puts those bytes into network packets which arrive at the LAN port of your PC instead of a serial port. I assume the format of those packets is proprietary since it must not only transport the raw byte stream from the GPS device but also the levels of the GPS devices serial control lines. The NTP program can only receive NTP packlets from another NTP server, not those proprietary ADAM packets. On the other hand, if you configure the NTP daemon on your PC to use the GPS device as a reference clock (as you would do without the ADAM) then ntpd tries to open the configureed serial port, set the baud rate etc. correctly, and receive the string from the GPS device. So if you want ntpd to read the serial time string from the GPS device then you have to install a driver on the PC which receives the proprietary network packets sent by ADAM, and appears like a serial device to the NTP daemon. Those drivers are normally shipped with the device, at least for Windows where they emulate a COM port e.g. COM20. You should see if the ADAM device comes with a Linux driver at all. And, please remember that network redirection of serial data introduces additional jitter, so the results may not be too good. Martin -- Martin Burnicki Meinberg Funkuhren Bad Pyrmont Germany ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Is there a document that describes the recommandation for configuring ntp ?
Hi Thierry, Thierry MARTIN wrote: > Hi all, > > Many of you kindly answered my previous questions, thanks a lot for that. > > Now I realise that I got a lot of "tips", that might be included in a > "recommandations" doc. > > So my quesiton becomes: > > Is there a document that describes the recommandation for configuring ntp? The best place to look is the NTP support wiki at http://support.ntp.org/bin/view/Support/ which covers many aspects of NTP configuration. > I mean -for instance-, it seems that "everybody" here knows that a > configuration with only two ntp sources should be avoided; so is there a > doc where I can find this kind of information? This particular topic is covered at http://support.ntp.org/bin/view/Support/SelectingOffsiteNTPServers#Section_5.3.3. That section also teaches why even 3 time sources may not be appropriate, and using at least 4 is a better choice. Martin -- Martin Burnicki Meinberg Funkuhren Bad Pyrmont Germany ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
[ntp:questions] Is there a document that describes the recommandation for configuring ntp ?
Hi all, Many of you kindly answered my previous questions, thanks a lot for that. Now I realise that I got a lot of "tips", that might be included in a "recommandations" doc. So my quesiton becomes: Is there a document that describes the recommandation for configuring ntp? I mean -for instance-, it seems that "everybody" here knows that a configuration with only two ntp sources should be avoided; so is there a doc where I can find this kind of information? Regards Thierry MARTIN ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] ntpdate.c unsafe buffer write
"David L. Mills" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] >>> No, there is no random delay at startup. Each association starts one >>> second after the previous one. The random backoff occurs only after >>> a step. >> >> Is there also a random backoff after an increase of the polling >> interval? > No. However, there is a small dither of a few percent at all poll > intervals to resist self-synchronization. Wouldn't that be a nice feature to add? If it's currently polling a server on, say second 100 (reckoned externally) of 256, to go to either 100 _or 356_ of 512. I understand that there are already some random waits in the client code and Internet servers are well protected by random noise. But for large numbers of clients in a uniform environment that were all started at about the same time, is there any way they tend to naturally disperse across the final 1024s polling interval? Groetjes, Maarten Wiltink ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Starting ISC NTP -4.2.4
Hi Thanks for the quick response. Yaa I did make install, even I copied the default startup script too, but its not working. I will check the log messages and check if its showing some errors Regards Vivek Aggarwal -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Hal Murray Sent: Wednesday, February 13, 2008 1:41 PM To: questions@lists.ntp.org Subject: Re: [ntp:questions] Starting ISC NTP -4.2.4 >Iam trying to install ISC NTP-4.2.4 on RHEL 4. But Im not able to start >the services. >I firstly removed the default rpm and then compiled the latest version, >configured the ntp.conf file, but Iam not able to start the service. I >give the command /etc/init.d/ntpd start. # prompt comes back. >Can anyone guide me in figuring out and solving the problem Did you do a make install? Do you even have a file in /etc/init.d/ntpd? I expect the old one came from the rpm and it probably didn't get replaced by anything from the ntp source package - those things are too system specific. Did it give any error messages? They usually end up in /var/log/messages unless/until you switch them to another log file with a logfile command in your config file. /etc/init.d/ntpd is just a shell script. You should be able to debug it. (It might take a while if you haven't worked in that area before.) Use "echo xxx" as the printf equivalent. "echo $foo" will expand foo from the environment variables. -- These are my opinions, not necessarily my employer's. I hate spam. ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] Starting ISC NTP -4.2.4
>Iam trying to install ISC NTP-4.2.4 on RHEL 4. But Im not able to start >the services. >I firstly removed the default rpm and then compiled the latest version, >configured the ntp.conf file, but Iam not able to start the service. I >give the command /etc/init.d/ntpd start. # prompt comes back. >Can anyone guide me in figuring out and solving the problem Did you do a make install? Do you even have a file in /etc/init.d/ntpd? I expect the old one came from the rpm and it probably didn't get replaced by anything from the ntp source package - those things are too system specific. Did it give any error messages? They usually end up in /var/log/messages unless/until you switch them to another log file with a logfile command in your config file. /etc/init.d/ntpd is just a shell script. You should be able to debug it. (It might take a while if you haven't worked in that area before.) Use "echo xxx" as the printf equivalent. "echo $foo" will expand foo from the environment variables. -- These are my opinions, not necessarily my employer's. I hate spam. ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
Re: [ntp:questions] ntpdate.c unsafe buffer write
Hal Murray wrote: > 20 ms sounds like a typical DSL link. That 1ms accuracy goes out > the window if you are doing a big download. (At least on my DSL > link.) > People don't generally do big downloads during the boot of a machine! On a big network, the most likely reason for rebooting a timeserver in prime time is a power failure. In which case the whole network is likely to be down. At worst, using ntpdate -b, you only get something like the current ntpd behavour. Typically you end up within a millisecond. ___ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
