Hi Even on good networks, getting below 1 ms with NTP is problematic. Yes indeed I have a heard of servers that will go below one us on a local LAN. That all breaks down pretty fast ( like under a dozen hops ) once you are on the Internet. 10 to 100 us is only going to work on NTP with local nets and symmetric routing.
Bob On Feb 20, 2012, at 8:44 PM, paul swed <[email protected]> wrote: > Even if the path is mapped the ques in the switches can change. Say your > packet is first and the next trip its the 50th. Just depends on the overall > network loading. > This has been tried many times and there is the ability to get a feel on > the timing. But not like GPS. > Regards > Paul. > WB8TSL > > On Mon, Feb 20, 2012 at 8:40 PM, Chris Albertson > <[email protected]>wrote: > >> On Mon, Feb 20, 2012 at 12:13 PM, Brooke Clarke <[email protected]> >> wrote: >> >>> You may be able to do a similar thing in your receivers. For example if >> the >>> master node were to send a timing message at known times (say once at the >>> top of every hour) the receivers could use that to determine their local >>> clock offset and rate for those cases where the path was the same (or >> maybe >>> even for a list of paths). The offset and rate numbers can be used to >>> correct the measured time to actual time without changing the clock's >> rate >>> using simple math. You can trade the receiver clock stability for the >> time >>> between the timing messages. >> >> >> So you are suggesting a very simplified version of NTP. I doubt you'd >> do better than using real-NTP. >> It turns out the method works at the millisecond level but not at the >> uSec level unless "everyone" is on the same local Ethernet >> >> There is one way to improve timing but it only works if you have >> control of all the network equipment. This means it can't work on >> the Internet but it can work on some large networks. Use "PTP". >> This is a little like NTP in that it uses a network for time >> distribution but has a slightly different method. Unlike NTP, for >> PTP you need special routers and switches built to support PTP but >> then PTP can support uSecond level timing over a wide area and NTP >> mostly can't >> http://en.wikipedia.org/wiki/Precision_Time_Protocol >> >> Chris Albertson >> Redondo Beach, California >> >> _______________________________________________ >> 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. _______________________________________________ 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.
