On 7/26/05, Tzafrir Cohen <[EMAIL PROTECTED]> wrote: > On Mon, Jul 25, 2005 at 06:19:02PM +0300, Ehud Karni wrote: > > On Mon, 25 Jul 2005 00:36:42 +0300, Amit Aronovitch wrote: > > > > > > Geoffrey S. Mendelson wrote: > > > > > > > I am a Nevtvision customer, they use a GPS unit to give them a stratum > > > > one server. I would avoid the overloaded server at HUJI if at all > > > > possible. > > > > > > Netvision here too - but I see them as stratum 2. > > > I sync to ntp.netvision.net.il (+ 2/3 times europe.pool.ntp.org for > > > backup). > > > Do they have another address for the GPS machine? > > > > You can use ntp.ilan.net.il (aka ntp.net.il) - startum 1 (using lab > > atomic clocks - not GPS - I think it is more accurate). > > Isn't that the "overloaded HUJI server"?
A reverse lookup confirms it's good old relay.huji.ac.il. > > > > > > Stratum 2 Israeli ntp servers: timeserver.iix.net.il , openu.ilan.net.il . > > And the netvision server. All seem to sync from that startum 1 server at > HUJI. > > Any other ISP that provides an ntp server? As long as these stratum-2 servers sync to DIFFERENT multiple NTP servers from each other (they may share some, but each one should have at least one server not shared by at least one of the other servers, i.e. the union of the servers they sync to should be different from the intersection of them all) they should be good enough. If you need a higher and more reliable accuracy (I hardly believe it) or in case you want it to be independent on your network connection - just buy a GPS PCI card or a simple GPS unit that can take an external antenna and external power source and connect via aserial line (there just might be USB-based units today, I haven't seen many, and anyway a serial line might be more reliable (i.e. predictive speed) for this job, since the NTP server can take into account the time it takes for the signal to travel accross the cable too). They're are not that expensive these days. And BTW - the atomic clock at HUJI should be more accurate than the GPS clocks, at least ten years ago - it was made of 3 cesium clocks and 5 GPS's inter-syncing and periodically (once a month) adjusted to earth's rotation based on measures collected in the US (navy?) from all over the world. It had an accuracy of 10e-13 of a second, as far as I remember the military-grade GPS signal (which wasn't available outside the US military back then) isn't more than 10e-12 of a second accurate (civilian signal's accuracy was 10e-8 or 10e-9, AFAIR). Anyway - the clock at HUJI was the most accurate one on the entire NTP network back when it was connected to the internet (it was the only one showing "ATOM" as its source :). Maybe it was upgraded since. If someone can bother someone from HUJI CS system group, it would be interesting to hear an update. Cheers, --Amos (former time master) ================================================================To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
