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

Magnus Danielson magnus at rubidium.dyndns.org
Thu Mar 20 19:49:49 UTC 2014


On 19/03/14 10:50, Miroslav Lichvar wrote:
> On Tue, Mar 18, 2014 at 10:20:08PM +0100, Magnus Danielson wrote:
>> 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).
>>
>> Doing HNTP makes NTP match up against PTPv1 to some degree, but PTP
>> then pulls out the explicit means to make PTP-aware transparent
>> clocks to correct for delays, cancelling some of the asymmetry. You
>> could do NTP with PTP 2-step processing, but what we would call such
>> a bastard would be an interesting thing, NPTP?
>
> There is already a "two step" mode implemented in ntpd that works with
> NTP peers or broadcast, it's activated by the xleave option.
>
> An NTP transparent clock could be implemented too. One problem is that
> with the current protocol it would have to track the connections. For
> a stateless operation a new NTP extension field would probably be needed.
> Similarly to PTP, all NTP-aware routers and switches between NTP
> server and client would increment a path delay correction.
>

Interesting!

NTP aware routers and switches is probably less common than PTP aware ditos.

Cheers,
Magnus


More information about the questions mailing list