Hi Any CDMA device is a *really bad* idea. It’s perfectly legal to run CDMA several seconds out of sync with UTC. There are a number of networks that do exactly this.
PTP is fine as long as *all* your network infrastructure (switches / hubs / routers) is PTP enabled. If any of your links are not fully PTP stamping devices you will get into time issues as your network load varies. Bob > On May 13, 2015, at 5:44 PM, Tucek, Joseph <[email protected]> wrote: > > In response to Oz-in-DFW > >> Given your description here, I'm guessing a millisecond or ten >> will do that as long as local cluster relative accuracy is maintained. > > Spot on; I hope I'd made it clear earlier, but perhaps I've been > communicating poorly. My goals w.r.t. to sync to UTC and w.r.t. holdover are > very loose. > > I do need time sync intra-cluster to be tight (sub millisecond, 100 nano as a > stretch goal). UTC sync can comparatively be terrible; 10-1 ms is fine, and > I can live with "bad NTP, 100 ms" if I must. From specs, */really/* good > quartz is my limit and /good/ quartz is acceptable, so long as it doesn't > mess with the intra-node PTP tightness. I'm mostly looking at TCXO options. > OCXO isn't out of the question, but rubidium doesn't seem to give $/value. > >> Yes, the master will have a fairly low phase noise local oscillator as >> it's internal reference. Everything will synch to that. If all you are >> doing is syncing the local cluster you don't even care about time >> outside. This is true for most industrial applications that are just >> syncing machinery. > > Thanks for the info. PTP isn't as well understood/documented as NTP, so I've > not been as certain about my decisions. Of course, that is fair for a > relatively new standard. > > Currently, I think my two best options are: 1) CDMA enabled PTP appliance > (set and forget), or 2) PTP appliance running as stratum 2 from good NTP. > > Thanks to everybody for the feedback. > > -joe > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
