Danny, Your comment on another thread about weather modelling stirred my pot. I gave a long thought about modelling when designing the synthetic sources for the ntpd simulator. With the Allan characteristic in mind the synthetic sources use exponentially distributed phase noise plus random-walk frequency noise, which nicely models the Allan characteristic shown in my papers and others.
But, that's kid's stuff. The real ornery cases can't be explained this easily. The best examples I have were when ARPAnet was operating really badly, but nobody knew why. It turned out routes were flapping between landline and satellite paths, as confirmed by the NTP rawstats wedge scattergrams. The scattergrams showed four overlapping wedges, each corresponding to one possible combination of landline and satellite links on each direction. Another interesting case was the early Internet path via the Atlanic to Italy, which had frequent glorious flaps over one second. For that matter the huff-n'-puff data shown in das Buch are wonderful grist for the NTP mill. Once upon a time earlly in Internet times Bob Braden at UCLA operated a "flakeway" best described as a route deflector that scattered incoming packets to random destinations. It was used as for testing TCP and routing algorithms. We need a similar package that can operate as an NTP server and do various kinds of timequakes for testing. Dave _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
