[chrony-users] Hardware time stamping and PHY specific features

[Pascal Regache <pascal@xxxxxxxxxxxxxx>]

Hello,  having to implement NTP with hardware time-stamping, I am looking for information on how things are done down at the PHY level.

I have to apologize first: I have tried to find the information through a web search only without much success (did not looked at the code). So the information might be available, I just didi not find it.

My guess so far is that it might rely on specific PHY PTP engine capability to recognize NTP UDP packets and capture the local clock timestamp (further processed by the PTP stack).

Still, PHY PTP engine usually look at the PTP message ID as well (not in NTP packets) and possibly other fields to trigger the local time capture.

But my guess could be totally wrong ....

So my questions are:

• Is there a detailed description somewhere on how it works down at the PHY level with NTP packets (I am a bit familiar with PTP engine in  PHY) ?
• What are the minimum PHY  set of features required for the mechanism to work ?

Thank you for the support 

Best regards 

Pascal