Re: [Linuxptp-users] How to use PTP for accurate relative time accuracy (when doing local timestamping) instead of absolute time accuracy?

[Miroslav L. <mli...@re...>]

On Mon, Mar 04, 2019 at 10:25:53AM +0000, C. Devereaux wrote:
> Could you please suggest the syntax of the phc2sys and ptp4l commands to run on server3  (time master) and server1? I will edit my systemd services to match. Server3 talks to server1 via eth1, which is called eth3 on the other end, on server1.

On the PTP master you could try this:

ptp4l -m -i $ETH --clockClass 6
phc2sys -a -r -r -P 1e-4 -I 1e-8

The system clock should be synchronized, e.g. by NTP.

The slaves can be configured by timemaster using both NTP and PTP.

> Because weak PI servo, or the constants I should use are not exactly self evident for a PTP beginner – and likewise for which algorithms will give the most accuracy. Based on my readings, I assume a stable jitter around 50 ns should be possible.

With good switches with PTP support jitter of 50 nanosecond might be
possible.

-- 
Miroslav Lichvar