Richard B. gilbert wrote: > Spoon wrote: > >> Richard B. gilbert wrote: >> >>> Spoon wrote: >>> >>>> I've read this page: >>>> http://ntp.isc.org/bin/view/Support/HowToCalibrateSystemClockUsingNTP >>>> which explains how to let NTP determine the frequency offset (skew). >>>> >>>> I have a strange request: >>>> >>>> Is it possible to run NTP in a mode where it does not try to correct >>>> the time offset, but only correct the frequency offset (skew)? >>>> >>>> In other words, assume my clock says it is some time last year, and >>>> gains 1 second every day (11.6 ppm). I don't want NTP to either slew >>>> or step my clock to the correct time, but I still would want it to fix >>>> this 1 s per day (11.6 ppm) frequency offset. >>>> >>>> Has this ever been considered? >>> >>> What problem are you trying to solve? >>> >>> Most people want the correct time rather than simply a clock keeping the >>> wrong time but one that ticks at one second per second. >> >> I'll try to explain my situation in detail. >> >> Consider two systems, A and B. >> >> A sends ~1000 UDP packets per second to B. >> >> A timestamps each packet. >> >> These packets travel over an IP network, and suffer delay and jitter. >> >> B is supposed to re-send the packets it receives at the rate they >> were originally sent by A. >> >> B buffers N packets. Then it sends the first packet in the queue, >> computes the departure time of the next packet using the timestamps >> provided by A, and sleeps until that departure time. >> >> If the clocks on A and B do not tick at the same rate, the buffer used >> by B will either overflow or underflow. >> >> This is why I need A's clock and B's clock to tick at the same rate. >> >> But it is not important to me that A and B's clock give the same >> absolute time. Was that clear or did I forget something important? > > ntpd should be able to both keep your clocks synchronized to the same > time but also to the same rate. There WILL be startup transients but > once the two machines are synchronized they should both have the same > time, within a millisecond or two and be ticking at 1.000000 seconds per > second.
If I start ntpd when the system boots, and let it run 60-90 minutes before I start my application, then this solution works very well! However, my boss thinks it is unacceptable to have to wait so long to start the application :-( > Is there some good reason why A's packets must be relayed through B? > Does B do any processing of the packets or does it simply forward them? B sends the packets it receives to a local device. Why do you ask? Regards. _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
