[ntp:questions] IEEE 1588 (PTP) at the nanosecond level?

Martin Burnicki martin.burnicki at meinberg.de
Wed Mar 19 09:43:09 UTC 2014


Magnus Danielson wrote:
> On 18/03/14 10:17, Martin Burnicki wrote:
>> We have mades some tests and found that NTP can yield the same accuracy
>> as NTP if also hardware timestamping of NTP packets is supported on all
>> nodes, similar as for PTP.
>>
>> In fact this isn't surprising, is it?
>
> No, it's not. NTP is being perceived to be "software timestamping" but
> nothing prohibits you from doing it in hardware. Similarly can you
> implement PTP with software time-stamping (with shitty performance).

As I mentioned in a different posting, even if you use hardware 
timestamping with NTP you are out of luck for highest accuracy since 
there are (AFAIK) no switches which have been designed to timestamp NTP 
packets.

And even if there were, the next question is how to get the measured 
latency compensation parameters to the client without breaking the 
existing protocol?

Maybe this would be an interesting approach for NTP v5.

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany



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