[ntp:questions] Slow convergence loopstats (but nice results)

Terje Mathisen terje.mathisen at tmsw.no
Tue Dec 10 07:34:48 UTC 2013

schmidt.rich at gmail.com wrote:
> My new prototype driver refclock_phc() uses as its clock the PTP
> Hardware Clock (PHC) found on one of the newer LAN NICs which are PTP
> (IEEE 1588) aware. This driver is producing phenomenal results (under
> LINUX 3.12 with linuxPTP): the overlapping Allan deviation computed
> from loopstats phase offsets alone reaches a stability of 6e-12 in
> under 2e5 seconds, and the modified Allan deviation reaches 2e-13.

This is extremely nice!

Do you use the PTP hw to also timestamp actual ntp packets, or just the 
onboard tcxo (or whatever the LAN card osc is) as a stable time base?

> This is quite useful, as eventually most all NICs will be
> PTP-enabled, and can be used as slaves as above, or even GrandMasters
> (with GPS, for example).
> I will ship my driver to Network Time Foundation when it is
> completed. This is a practical realization of PTP-NTP partnering in a
> refclock driver! Regards, Rich Schmidt

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