Hi, So to summarize you guys. I think that you are saying that ntpd v3 is accurate on a gigabit network that is congested to 5-20ms is the accuracy is a reasonable expectation. What about IEEE 1588, since this is also ethernet bases can I get any better time accuracy with that?
"Richard B. Gilbert" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Bjorn Gabrielsson wrote: > >>"Richard B. Gilbert" <[EMAIL PROTECTED]> writes: >> >> >>>K wrote: >>> >> >> >>>>I know about NTP v3 and v4 and use it on some systems. I need a time >>>>accuracy of < 1 ms. >>>> >>>>I know that the linux os is compiled for something like 1 ms precision >>>> >> >>? >> >>>So it can be done. I think that the Motorola GPS has a great deal to >>>do with it. >> >>The motorola should carry you down towards 1us, but K was only asking >>for a thousand times less accuracy... :-) >> >> >>>clock would be much less stable. 10 ms is about the best accuracy I >>>would expect from a client synchronized to a server that synchronized >>>over the internet. >>> >> >>Even with a DSL-line - if its not overloaded - sub 1ms is easily >>attained with good internet servers. Looking at a machine with four >>external servers, I get see, >> >>/usr/sbin/ntpq -c pe >> remote refid st t when poll reach delay offset >> jitter >>============================================================================== >> LOCAL(0) 73.78.73.84 5 l 25 64 377 0.000 0.000 >> 0.001 >> xxx .PPS. 1 u 219 256 377 11.476 -0.235 >> 0.779 >> xxx .PPS. 1 u 102 256 377 17.818 -0.140 >> 75.660 >> xxx .PPS. 1 u 217 256 377 21.575 0.203 >> 0.235 >> xxx .PPS. 1 u 192 256 377 20.889 0.385 >> 0.142 >> >>This machine usually have two GPS-refclocks and they show no >>systematic offsets wrt the Internet servers. >> >>-- >> >> Björn >> > Either your internet connection, your internet servers, or both are far > better than mine. I have broadband cable. My NTP server, Sunblok, uses > five internet servers in addition to the Motorola GPS reference clock. > The internet servers show systematic offsets with respect to GPS of +1 to > +5 ms. There are also seemingly random spikes in the time received from > the internet servers of +/- 5 to 20 ms. When the GPS is not running, ntpd > tends to synchronize with a different server every few minutes which does > nothing for the stability of the clock. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
