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- To: chrony-dev@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-dev] SW/HW timestamping on Linux
- From: Denny Page <dennypage@xxxxxx>
- Date: Wed, 07 Dec 2016 23:04:42 -0800
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On the offset issue… one of the benefits of having so many ports, and several of hardware based NTP units (thanks Leo/Anthony!) is that I have been able to replicate the issue by connecting serval ports directly from host to host with and without an intervening switch. I’ve also been able to test different chipsets. The short version of all the tests is that there is clear asymmetry with hardware timestamps. Based on research and the fact that the asymmetry varies with chipset, my best guess is that the hardware tx/rx timestamps are incorrect and need compensation in the driver. The 4.8.X kernel introduced compensation for the i210, but not for the i211 or the i354 (which I am testing with). I have a query into the Intel folk about this and will let you know what they say.
Denny
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