[time-nuts] Precision Time Protocol – Windows 10 implementation

[Adam Kumiszcza]

On Thu, Aug 8, 2019 at 7:01 PM Tim Lister <listertim at gmail.com> wrote:

> On Thu, Aug 8, 2019 at 8:07 AM Adam Kumiszcza <akumiszcza at gmail.com>
> wrote:
> >
> > Hi everybody! My first post here, I hope the subject is adequate for this
> > mailing list.
> >
> > I'm using a tiny layer 1 NTP server consisting of Raspberry Pi 3B+ with
> > Ublox MAX-M8Q expansion board providing GNSS (currently GPS, Galileo and
> > Glonass, sometimes I switch to Beidou, too) reference with PPS + a simple
> > patch antenna hanging near the window. Offset, jitter and rms are most
> > often smaller than 1 µs. The server is included in NTP pool.
> >
> > I'm using several Windows 10 machines on the same LAN, all using NTP
> client
> > software from Meinberg. The typical offset and jitter in those are about
> > 100-500 µs. I would like to make it lower. I've heard that one of the
> > latest versions of Windows 10 provides support for PTP protocol (IEEE
> > 1588v2). Hence my questions:
> >
> > 1. Did anybody try using it on Windows 10 already? From what I can tell
> > right now, there's only a demonstration web site showing it works when
> > using Ubuntu Linux as a virtual machine [1]. Or should I wait a bit for
> > more robust implementation?
>
> EndRun Technologies
> (https://endruntechnologies.com/products/grandmaster-clocks/ptp-slaves)
> make mention of a Windows PTP slave - not sure if it's the same
> version you have found. It does also make mention of the fact that
> precision is limited on Windows depending on version although from
> what I gather from the satsignal.eu that precious on Windows improved
> with 7 or later.
>

It's additional software here. As far as I understand, recent Windows 10
versions introduced under-the-hood internal implementation of PTPv2, with
kernel support for it.


> > 2. Do I guess correctly that current implementation of PTP works only on
> > Ethernet? Some of the computers are on wlan.
>
> For deterministic timing I think it has to be Ethernet and as outlined
> in their white paper (https://endruntechnologies.com/pdf/PTP-1588.pdf)
> it works best if you have hardware timestamping in the NICs at each
> end and IEEE1588 compatible network switches (and even when the claim
> to support it, apparently they don't always do it properly:
>
> https://www.linkedin.com/pulse/ptp-support-high-end-ethernet-switches-heiko-gerstung
> ).
> You may be able to do some Pi-to-Windows PTP experiments with a
> crossover cable. Not sure if the Pi has the hardware timestamping,
> seems unlikely given the low cost of the Pi's as in the 3B+ (and below
> I believe) the Ethernet is provided by a combined Ethernet/USB2 hub
> and limited by the speed of the USB2.
>

Pi 3B+ has only software timestamping, and even this is not completely
clear (I had to patch the kernel). Pi-to-Windows direct crossover testing
is a great idea!

Best regards,
Adam