[time-nuts] Best Chance GPS module

Gian-Paolo Musumeci gp at pdti.net
Thu Dec 1 22:54:34 EST 2016

On Thu, Dec 1, 2016, at 09:01 AM, Chris Albertson wrote:
> The other thing you might look at is NOT using NTP but using PTP.   This
> might be a better match to your needs but it requires that you replace
> all your network gear with equipment that can make hardware time stamps
> on the network packets.

You don't actually need to have PTP-capable network gear to make PTP
reasonably well.

I have a small test environment with a Symmetricom S300-Rb PTP
distributing time to six Cisco UCS blades running FreeBSD. The S300 does
hardware timestamping, but the UCS blades do not. The network has a
UCS fabric switch plus an Arista 7124S, neither of which support PTP
transparency. Works fine; I haven't measured it exhaustively, but
data suggests that I am getting 2.5e-5 seconds of drift in the worst

I've heard reports that full hardware timestamping and transparent
can easily get you into the 1e-7 range, but I haven't tried that yet.

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