On 2011-09-01, Miguel Gon?alves <[email protected]> wrote: > Hi! > > Thanks for your reply. My comments bellow. > > On 1 September 2011 18:24, unruh <[email protected]> wrote: > >> On 2011-09-01, Miguel Gon?alves <[email protected]> wrote: >> > Hi all! >> > >> > I have two internal FreeBSD with GPS receivers attached (Garmin 18 LVC: >> > 10.0.2.10 / Sure Evaluation Board:10.0.2.9). Both machines are on the >> same >> > LAN segment (VLAN). >> > >> > For redundancy, I've configured a Cisco switch as a stratum 2 server. >> Here's >> > the relevant information: >> > >> > $ ntpq -pcrv 10.0.2.254 >> > remote refid st t when poll reach delay offset >> > jitter >> >> >============================================================================== >> > +ntp0.as34288.ne .PPS. 1 u 814 1024 377 72.750 -1.084 >> > 0.780 >> > +canon.inria.fr .GPSi. 1 u 399 1024 377 55.110 0.218 >> > 0.400 >> >> What are those machines? You have names rather than IP addresses. >> Are they your pps machines? > > > No. This is a stratum 2 server and it gets the time from stratum 1 servers > thus the names and not IP addresses.
What I am asking is what the mapping is between these names and the numbers you have later. I assume that some of those names are the same machine as the IP addresses you list below but We do not have that infomation. > > > I have another machine (Linux, CentOS 5.6) that is a client to these >> stratum >> > 1 FreeBSD machines. Here's the relevant information: >> > >> > $ ntpq -pcrv 10.0.2.2 >> > remote refid st t when poll reach delay offset >> > jitter >> >> >============================================================================== >> > +10.0.2.10 .GPS. 1 u 211 256 377 0.159 -0.139 >> > 0.350 >> > *10.0.2.9 .GPS. 1 u 71 256 377 0.166 -0.136 >> > 0.468 >> >> That is a huge offset for being on the same lan, and for being only >> .15ms away. > > > It's really strange... I am getting on another LAN connected to this one > these values... > > $ ntpq -p 10.0.99.99 > remote refid st t when poll reach delay offset > jitter >============================================================================== > *10.0.2.10 .GPS. 1 u 21 256 377 0.173 0.196 > 0.008 > +10.0.2.9 .GPS. 1 u 93 256 377 0.175 0.191 > 0.014 > +10.0.2.254 81.94.123.16 2 u 149 256 377 0.583 -6.884 > 0.152 > > This is a FreeBSD embedded PBX machine running Asterisk. The machine is > mostly idle. What kind of offsets should I get with local machines? in the 10s of usec range max. Certainly less than the delay. > > Here in Portugal our Time Dissemination Authority has two stratum 2 servers. > One of them shows this: > > $ ntpq -p ntp02.oal.ul.pt > remote refid st t when poll reach delay offset > jitter >============================================================================== > *ntp01.oal.ul.pt .GPS. 1 u 113 128 377 5.125 -0.263 > 0.320 > ntp03.oal.ul.pt .INIT. 16 u - 1024 0 0.000 0.000 > 0.000 > -ntp04.oal.ul.pt 194.117.9.138 2 u 57 128 377 0.377 -0.056 > 0.080 > +ntp05.oal.ul.pt .GPS. 1 u 62 128 377 0.296 0.128 > 0.058 > +ntp06.oal.ul.pt .IRIG. 1 u 56 128 377 0.310 0.104 > 0.045 > > Assuming ntp04, ntp05 and ntp06 are on the same LAN I see offsets higher > than 100 us. Is it possible to decrease these numbers? Sure. all my systems have offsets in the 10us range-- on the same lan as my time server. Mind you I do use chrony, not ntpd but even ntpd should be in a few 10s of usec. > >> tick# ntpdate -p8 -q tock >> > server 10.0.2.9, stratum 1, offset -0.000004, delay 0.02577 >> > 1 Sep 10:23:45 ntpdate[3537]: adjust time server 10.0.2.9 offset >> -0.000004 >> > sec >> >> That probably says more about the symmetry of the path than the offset >> of the machine. > > > OK. But this is a 24 port Gigabit switch from Cisco. I wouldn't expect > asymmetry but it could be. > > > Are my GPS clocks OK? Does this happen due to the network latency? Are my >> > stratum 2 servers OK? >> >> Your GPS seems to be consistant with each other ( that is all one can >> say without another time source to compare them to). Your offsets are >> large compared with the delay times ( was the machine recently heated >> up due to working harder?) > > > All these machines sit in a room temperature controlled at 20 ?C. 10.0.2.2 > is a backup server that just does some work every hour but nothing huge. > > 10.0.2.2 has been running for quite a while and it doesn't seem to get lower > offsets. Could it be because it's running Linux? I've heard Linux is not as > good as FreeBSD for time keeping. All my machines are Linux machines. Linux is fine for timekeeping. > > Thanks! > > Regards, > Miguel _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
