Thank you very much Mr de Raadt, for the very complete and insightful information regarding GPS & the interaction and actions of clocks with their signal, and loss thereof.
On 3/20/2012 11:49 AM, Theo de Raadt wrote: >> some insights for people using GPS for very critical server time keeping >> http://www.dw.de/dw/article/0,,15817272,00.html > This misses the point in a rather large way. > > Most of this jamming makes the true GPS signal hard to receive. > > When the signal cannot be received, the existing free-running clocks > in various parts of the "system" keep working. Since the subsystem as > a whole has learned the 1st, 2nd, and hopefully 3rd and further > derivatives to tune itself and predicively pace, everything works out. > Until the GPS signal or whatever else comes back. > > Oh my god, sometimes we use net, and we can't talk to remote > Internet-based ntp services. Except that's the point -- we only pay > attention to the remote services (ntp or gps) to learn how to tune > various adjustments to the free-running clocks. > > Furthermore, some GPS receivers will keep feeding their own > free-running clocks but say the service is "degraded". It is not like > that free-running clock on the GPS is going to go wonky immediately. > > It is being jammed. It is not being spoofed. > > The end result is that the clock does not go crazy. It remains stable > and the best effort result is good enough. > > So enough of this "oh my god, it is all going to go wrong" balony.
