[ntp:questions] ntp on ubuntu 12.10 with gps and pps.
Hi All, I've got a SiRF star 3 GPS with a PPS line which im trying to get running on a machine with ubuntu 12.10 and a serial port using the DCD line for pps signalling. Took quite a while as the ntpd that ships with ubuntu 12.10 appears to be compiled without pps support (please correct me if im wrong here - but no matter what I do, the shipped version never tries to open /dev/pps0, gpspps0, etc etc and i've checked permissions and apparmor) - also theres alot of contradictory info on the net about how you get pps and gps operating this way (took some time to find that i needed flag1 1 in the gps settings - which alot of articles dont mention). But, once it was up and running it appeared to work very well, after a few hours the jitter was down to below 0.01. Next I added in a few external time sources, and i ended up with this: remote refid st t when poll reach delay offset jitter == 203.0.178.191 216.218.254.202 2 u 14 6438.704 990.003 0.189 (my isp) 203.82.209.217 18.26.4.105 2 u 18 643 62.372 997.624 0.466 (pool server) 202.127.210.36 223.255.185.22 u 19 643 22.454 1067.75 1.747 (pool server) 130.102.2.123 130.102.132.164 2 u 17 643 22.947 1000.23 0.392 (pool server) 202.125.45.77 223.252.32.9 2 u 17 643 24.810 1001.95 0.849 (pool server) *127.127.20.0.GPS.0 l78 3770.000 0.467 0.209 (GPS) Everythings almost exactly 1 second out. Reading around about this, it appears that this occurs cause theres possibly too many sentences coming across the 4800 baud serial line, is that correct? After adjusting fudge time2, i ended up with with this: remote refid st t when poll reach delay offset jitter == -203.0.178.191 216.218.254.202 2 u 51 64 3779.070 -5.518 1.423 -202.127.210.36 223.255.185.22 u 53 64 377 21.729 74.408 4.701 *203.192.179.99 223.252.32.9 2 u 48 64 377 22.956 17.581 3.551 +119.148.67.183 203.12.160.2 3 u 51 64 377 21.200 4.094 1.439 +203.192.179.98 203.35.83.2422 u 50 64 377 22.735 17.913 27.315 o127.127.20.0.GPS.0 l38 3770.000 5.080 0.193 and a few hours later: remote refid st t when poll reach delay offset jitter == +203.0.178.191 216.218.254.202 2 u 44 64 3779.041 -10.309 0.356 +202.127.210.36 223.255.185.22 u 50 64 377 21.547 64.812 6.039 +203.192.179.99 210.9.192.50 2 u 35 64 377 23.000 -0.256 2.525 -119.148.67.183 203.12.160.2 3 u 48 64 377 21.006 -15.580 4.364 -203.192.179.98 203.35.83.2422 u 49 64 377 23.130 74.392 26.231 o127.127.20.0.GPS.0 l48 3770.000 -0.065 0.003 and the config i've ended up with is: server 127.127.20.0 mode 1 minpoll 2 maxpoll 4 prefer fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 time2 1.0 Seems like a pretty decent little gps unit, assuming i've got it functioning and configured correctly? ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] ntp on ubuntu 12.10 with gps and pps.
On 07/04/2013 11:14, Paul J R wrote: Hi All, I've got a SiRF star 3 GPS with a PPS line which im trying to get running on a machine with ubuntu 12.10 and a serial port using the DCD line for pps signalling. [] o127.127.20.0.GPS.0 l48 3770.000 -0.065 0.003 [] Seems like a pretty decent little gps unit, assuming i've got it functioning and configured correctly? Just for comparison: Intel Atom PC running FreeBSD 8.2 (Pixie): o127.127.20.1.PPS. offset/jitter -0.001 0.002 Two Raspberry Pis running Linux 3.2.27+ o127.127.22.0.PPS. offset/jitter 0.002 0.002 o127.127.22.0.PPS. offset/jitter 0.001 0.002 Raspberry Pi running Linux 3.36.11 o127.127.22.0.PPS. offset/jitter 0.000 0.002 65 microseconds offset seems a little high to me, but the PCs I've just quoted are all (mostly) /only/ serving NTP. I have been doing a little installation work on Raspberry Pi #3 today, and it now has a steady CPU and network I/O load. Its PPS was only configured yesterday. Performance graphs are here: http://www.satsignal.eu/mrtg/performance_ntp.php I hope that helps your comparisons. -- Cheers, David Web: http://www.satsignal.eu ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Syncing and peering for a multi-continent deployment
I'm working on deploying a large number of servers to data centers on three continents, say US, Europe and India. Because each data center will be writing data and timestamping the data, I want them all to think they are at the same time, even if it isn't exactly the correct UTC time. The data will be synced to other data centers, so relative ordering of when something happened can be important. To not ping stratum-1 and -2 level servers from a large number of boxes, I'm setting up three stratum-3 NTP servers in each data center. Here's what I've read: 1) Each ntp server should have 4 to 7 upstream clocks [1], [2], [3]. 2) The three stratum-3 NTP servers in each data center should be peers of each other [4]. So each NTP server would have at most 2+7=9 connections. Questions: 1) Should each data center use nearby stratum-2 clocks or pick a set of stratum-2 clocks that are network wise in the center between all data centers (it may not be possible to get a true center)? 2) Should each stratum-3 server in a single data center use all 4-7 upstream clocks? Or should the 4-7 be split between the three stratum-3 servers? The diagram at [4] suggests they should be split? If that's the case, then how are falsetickers identified? 3) Should I have all the stratum-3 servers in each data center be peers of each other, so each would have 8 peers? This would ensure that all my clocks think they are at the same time. If I do this, then I would need to increase maxclocks to support up to 7 (upstream) + 8 (peers)=15 clocks? 4) Or, should I not peer data centers to each other and trust that the stratum-2 clocks near each data center will be close to the other clocks? Other random questions: 1) It doesn't appear that its necessary to set up symmetric keys for peers? 2) Is there a way to tell which peer is the master peer? Looking through ntpdc and ntpq I didn't see anything. Thanks, Blair [1] http://support.ntp.org/bin/view/Support/SelectingOffsiteNTPServers#Secti [2] http://support.ntp.org/bin/view/Support/SelectingOffsiteNTPServers#Secti [3] http://support.ntp.org/bin/view/Support/StartingNTP4#Section_7.1.4.3.2. [4] http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm#AEN3101 ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Syncing and peering for a multi-continent deployment
Blair Zajac writes: 1) Each ntp server should have 4 to 7 upstream clocks [1], [2], [3]. Each NTP server should have a GPS receiver. Fall back to the Internet if GPS goes down. -- John Hasler jhas...@newsguy.com Dancing Horse Hill Elmwood, WI USA ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
