Rick, Apparently, OWAMP uses NTP timestamps, but the article assumes there is a difference between "NTP time" and "system time". Statistically, NTP time is an unbiased estimator of UTC and system time is a lowpass version of it. The offsets you might consider NTP time represent statistical uncertanty of that estimate and should not be used as system time.
Now for one-way delay calculations, which I can't find in the article. In cases of severe one-way congestion, which might be the objective, see the NTP huff-n'-puff filter, which is designed to prize this out. As for swish and sway due to congestion, Chapter 6 of das Buch has a really interesting example of a path from here to East Asia with awesome one-way congestion. Huff-n'-puff sliced through it like butter. It could be that the statistical methods used by huff-n'-puff be useful if exported to other applications. Theoretically, you can't measure one-way propagation times unless you have some other measure such as bit rate. The first experiments to measure this was done 30 years ago using the ARPAnet and had some success. The code measures the data rate by launching packets of varying size and measuring the differential delays. I recently tried the same thing in my earlier experiments using the NTP daemon ntpd, but wasn't thrilled with the results. For the experiment to work right the network should satisfy what is called the Kleinrock Assumption, and my dinkly ISDN line to campus fails that assumption. Nevertheless, the code is in the ntp-dev version, but currently disabled. Dave Rick Jones wrote: > Ulrich Windl <[EMAIL PROTECTED]> wrote: > >>[EMAIL PROTECTED] (Kevin Oberman) writes: >>[...] >> >>>Netperf is not really the best way to go. The appropriate tool for >>>one-way latency is OWAMP. http://e2epi.internet2.edu/owamp/ > > >>I think you missed the point: AFAIK, Rick is the author of netperf ;-) > > > Shhhh! It's a secret!-) > > rick jones > > about to hit-up "management" for aproval to buy a GPS-18 for some > experiments, unless someone knows of a better device... > _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions