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- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] help - UTC time of PPS pulses
- From: Bryan Christianson <bryan@xxxxxxxxxxxxx>
- Date: Thu, 15 Oct 2020 00:19:14 +1300
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Hi Yoed
> On 14/10/2020, at 11:23 PM, Yoed Stavi <Yoed.Stavi@xxxxxxxxxxxxxxx> wrote:
>
>
> And possibly the offset that I've been measuring is due to transmission delay of the ASI card.
>
I built a similar system to yours about 20 years ago - an encapsulator for sending IP packets via geo-stationary satellites. The system was running under Debian with Linux 2.1 on relatively modest hardware. The lag introduced by the encapsulator and ASI interface was negligible compared to the that introduced by the satellite path. The receivers were running ntpd (this system predated chrony) and were able to keep very good time. We ran the same encapsulator/ASI over terrestrial links, again with similar results, although much improved latency. I agree with Miroslav's conclusion. Use chronyd to get the system clock as close to UTP as possible, then use the system clock on the encapsulator to derive the timestamps for the transport stream. Once the transport stream has left the ASI interface you have no controller over the transmission latency.
Bryan Christianson
bryan@xxxxxxxxxxxxx
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