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

Miroslav Lichvar mlichvar at redhat.com
Wed Mar 19 09:50:08 UTC 2014

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.

Miroslav Lichvar

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