Noob wrote: > Richard B. Gilbert wrote: > >> Noob wrote: >> >>> I've been running ntpd 4.2.4 to synchronize my system clock using >>> remote stratum 2 servers as a reference. (The RTT to these servers is >>> in the 30-50 ms range.) The accuracy is in the 1-2 ms range, based on >>> the reported offset. >>> >>> I've been asked to evaluate the following time server, in order to >>> reach a better accuracy than what the current setup provides. >>> >>> http://www.heoldesign.com/index.php?id=58 >> >> >> That link takes me to a page advertising THREE products! Which one >> did you have in mind? > > > The HEOL-T101 (with a Fast Ethernet port). > >>> Is it a problem that the time server only implements SNTP? >> >> >> It should not be a problem. The largest difference between NTP and >> SNTP is the effort to account for the vagaries of the internet! > > > Cool. (I'll give RFC 4330 a look.) > >>> What kind of accuracy may I expect? >> >> >> These devices should be accurate to within the range of 25 to 100 >> nanoseconds. > > > The spec seems to mention +/- 40 ns. > >> The limiting factor will be the jitter introduced while getting the >> time into your computer. > > > I plan to connect my box to the time server using a cross-over cable. > (My box has 4 Ethernet ports, I will devote one to NTP traffic.) The RTT > is very stable at 80-85 µs. > >> A SWAG (Scientific Wild Ass Guess) would be 500 microseconds. By >> spending a lot of time and effort you might be able to get something >> better than that. The chief difficulty would be measuring and >> controlling the delays within the computer. > > > I thought the error was on the order of half the RTT, i.e. I could hope > for 40-50 µs in my situation? > > Regards.
Given the above, you are correct, 40-50 microseconds. I had assumed that you were using a serial port where the latencies are greater. _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
