I respectfully do not agree that anycast is useless. I have used, not anycast, but multicast on my home (gigabit) LAN quite successfully. One server only on the LAN sees the time from external NTP servers. The other 3, 4, etc. ntp clients, which only existed to process SETI@Home work units, accessed their time from that server using multicast. The time differences between the clients were very small, but I can't supply a firm number, since I have switched to using FreeNAS as the time server connected to external ntp servers, and I have not had time to figure out how to make FreeNAS's NTP do multicast. In any case, the offsets and jitters of the ntp clients on the LAN were also extremely small. The Gigabit Ethernet LAN was/is very lightly loaded, and it is not connected to the Internet.
If anyone else tries this, I would urge them to read the reviews of Gigabit switches first. There are real differences in the switching speeds of these devices, and you may see these differences reflected in ntp delay statistics (when in unicast mode). Charles Elliott > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On > Behalf Of Rob > Sent: Friday, October 31, 2014 3:17 PM > To: [email protected] > Subject: Re: [ntp:questions] ntp and anycast > > Markus Moeller <[email protected]> wrote: > > Hi, > > > > What do I need to consider when using an anycast IP for a NTP > servers ? > > If I remember right a client should have at least 3 better 4 ntp > servers > > configured to identify the best sources, but if you use anycast IP > for a > > server the client would have only one server configured, so how would > the > > client find out any drift, bad time source ? > > > > Thank you > > Markus > > When you use anycast, you probably don't worry about that. > Anycast is good for "get an approxmate time" in environments that are > more like SNTP than NTP. E.g. to set the time of a home router. > > For keeping accurate time and using the kernel phase locked loop, > anycast is worthless. > > _______________________________________________ > questions mailing list > [email protected] > http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
