On 2012-08-08, Rick Jones <[email protected]> wrote: > I've scrounged a couple old Pentium M laptops (Hewlett-Packard nc6000s > for the trivia-minded) with serial ports while entertaining the > possibility of undertaking a project to do what so many others have > done - connect-up a GPS receiver with PPS support. That has me > wondering about some of the previous discussion about USB and how it > is perhaps not "evil" but considered quite sub-par for serving-up the > PPS signal. > > Is that unsuitability inherent in USB, so it matters not whether there > is anything else on the USB, or is it more a case of being "bad" > generally only when other things are on the same USB? I'm still > looking to go serial, but was wondering.
USB is packetized. > Also, speaking of things considered "bad" and drifting - fudging the > LOCAL(0) is definitely frowned upon right? The Undisciplined Local Clock (127.127.0.x aka "LOCAL") has a default stratum of 5. It is often recommended to fudge the Undisciplined Local Clock farther away from possible strata at which real time sources usually operate (e.g. to stratum 10). > If I happen to have say four servers in a location which might loose > its connectivity to the outside world I probably don't want those > servers to fall-back on LOCAL(0) right? This is an issue of systems architecture. Setting up all of your servers with the Undisciplined Local Clock at the _same_ stratum is a recipe for disaster because there will be no local master. You really only need one system in that cluster to be your "Time Island Master". The system with the most stable clock should be the only one configured with the Undisciplined Local Clock driver. > Would configuring each to have the other three as "peer" entities be > the way to go? I would configure the other three systems to be clients of the "Time Island Master". A more elegant solution is to set up your systems in an Orphan Mode "Mesh" (i.e. each node is a Server and a Client for whichever mode you choose.) Orphan Mode allows your group of servers to autonomously select a leader in the event no real time sources are reachable. Orphan Mode can be used with any association mode; broadcast, multicast, and manycast have the advantage of allowing you to use a common configuration file across all nodes and make adding/removing nodes a no-brainer. Automatic Server Discovery http://doc.ntp.org/4.2.6p5/manyopt.html Association Management http://doc.ntp.org/4.2.6p5/assoc.html Miscellaneous Options http://doc.ntp.org/4.2.6p5/miscopt.html -- Steve Kostecke <[email protected]> NTP Public Services Project - http://support.ntp.org/ _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
