Tony Hoyle wrote: > True, but since I've got a server in the pool I'd rather be as reliable > as possible... If using a remote stratum 1 is going to mean I'm a > couple of seconds out then it's not worth it - I'd rather not introduce > any *more* error than is already there. > > Adrian von Bidder wrote: >> reliability is an issue - and I guess stratum 1 and stratum 2 is not >> the correct question here. Stratum 1 run by some hobbyist on a DSL >> line won't be reliable, but stratum 3 used as main timeserver at a big >> university will usually be. (time[123].unizh.ch, for example) > > It comes down to.. which is more accurate: > > A stratum 2 in the UK: > > veracity.mcc.ac 193.63.105.18 2 u 354 1024 377 23.520 0.023 0.037 > > Or a stratum 1 in Germany: > > sombrero.cs.tu- .PPS. 1 u 500 1024 377 50.280 -0.473 0.202 > > OTOH you're saying this is more accurate (actually a stratum 2 not 3): > > rosehip.exnet.c 192.43.244.18 2 u 7 64 37 37.404 -5.812 1.827 > > ..which means I really don't understand how to interpret the figures.
The last three columns are the most relevant for determining what's the best reference server: "delay", "offset" and "jitter". They are given in milliseconds. > > ntpd itself says that the stratum 1 is the most accurate, and picks > it as a timesource. Stratum 1 servers have a preference over stratum 2 servers. > > My reading of the figures says that the UK source is most accurate, > having the lowest jitter, delay and offset. Low jitter is the most important of the three, low delay indicates that you have a good network connection and will see little network jitter. Offset is the paramater that ntpd will try to optimise to 0. It indicates that your clock and the peer clock are synchronized. Servers that show offsets far away from reality are best avoided: vrt-19.ams-2.th hora.cs.tu-berl 2 u 885 1024 372 25.609 1428.77 2957.34 (a jitter of >1 second is a giveaway!) > Now I'm really confused!! Is there a document that explains how to > interpret these figures? I hope you got some from my explanation. My suggestion is to handpick 5 to 7 good peers (relatively close, low jitter). Stratum 1 or 2 doesn't matter that much. Give your machine 2-3 days to sync (when deploying ntpd the first time) or one day after a reboot before judging the quality of your peers. Peter. _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
