[time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

shouldbe q931 shouldbeq931 at gmail.com
Thu Feb 16 12:59:19 EST 2017

On Thu, Feb 16, 2017 at 7:55 AM, Chris Albertson
<albertson.chris at gmail.com> wrote:
> But PTP requires special hardware.   You may not have this.

I have to disagree.

I run PTP on a Raspberry Pi using its onboard USB connected NIC, and
onboard NICs on HP and Dell servers, I see +- 5 microsoconds jitter in
the one way delay across 4 fanless HP switches, and when PTP is
running on a Pi with a GPS hat with PPS, I see +50 -30 microseconds
jitter in the reported offset from master across the slaves.

If the requirement is for sub millisecond then PTP on commodity
hardware is a _workable_ solution.

If sub microsecond accuracy is required, then the NIC, Ethernet switch
and time source hardware requirements change.


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