On 06/11/2015 08:41 AM, Kashif Mumtaz Tahir wrote: > Dear Jochen, > You extracted description is right , we are at stratum 2 and just syncing > its time with stratum 1 level GPS device. > > Litte bit confused with your conclusion. When leap second will happen on GPS > what will the impact on our stratum 2 level server and below beyond ( Straum > 3 client etc )
The part I cannot answer is whether (and when) the GPS device will forward the information about the upcoming leap second into the data it hands out via NTP. As an example, Meinberg states that their GPS receivers will start announcing the leap second during the last 59 minutes: https://www.meinbergglobal.com/english/info/leap-second.htm#refclocks and confirms that those units which also speak NTP will include the refclock's announcement in their replies: https://www.meinbergglobal.com/english/info/leap-second.htm#ntp-server So, *if* your GPS unit were a Meinberg LANTIME model, your stratum 2 server would be made aware of the upcoming leap second about one hour before it happens. Now, assuming that that *does* happen: ntpd *does* forward this information (because you have no leapsecond files overriding the info received from the server), and ntpds actually start polling their servers more frequently as the leap second slot draws near, so all devices running NTP (not SNTP) will typically have their OS "armed" (informed that it - the OS, not ntpd - will have to take action to conform to the leap second) in time. That implies that *how* they actually do that is up to every OSes' choices and implementation. The most usual *choice* is to have the OS clock stepped back one second, 23:59:59.999... -> 23:59:59.000... . And then there's the possibility that the code, which currently gets executed once every couple *years*, has a bug making it do *something else*. For (a historic) example, freeze the server. :-/ That's why having test machines go through a simulated leap second is a thing. (For sake of completeness, any client doing SNTP will notice a one-second offset the first time it contacts its servers after the leap second, and perform the step *then*. That should IIUC (still) include most of the machines running Windows.) Regards, J. Bern -- *NEU* - NEC IT-Infrastruktur-Produkte im <http://www.linworks-shop.de/>: Server--Storage--Virtualisierung--Management SW--Passion for Performance Jochen Bern, Systemingenieur --- LINworks GmbH <http://www.LINworks.de/> Postfach 100121, 64201 Darmstadt | Robert-Koch-Str. 9, 64331 Weiterstadt PGP (1024D/4096g) FP = D18B 41B1 16C0 11BA 7F8C DCF7 E1D5 FAF4 444E 1C27 Tel. +49 6151 9067-231, Zentr. -0, Fax -299 - Amtsg. Darmstadt HRB 85202 Unternehmenssitz Weiterstadt, Geschäftsführer Metin Dogan, Oliver Michel _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
