10000 Why is NeighborRateRatio not considered when measuring PTP path delay · Issue #91 · ptpd/ptpd · GitHub
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Why is NeighborRateRatio not considered when measuring PTP path delay #91

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liu-jeff opened this issue Aug 19, 2022 · 1 comment
Open

Why is NeighborRateRatio not considered when measuring PTP path delay #91

liu-jeff opened this issue Aug 19, 2022 · 1 comment

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@liu-jeff
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liu-jeff commented Aug 19, 2022 •
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Hello, I am very sorry to bother you , but I have some confusion about this, why is NeighborRateRatio not considered when measuring PTP path delay.
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@aaeegg
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aaeegg commented Jan 20, 2023

ptpd calculates meanPathDelay according to IEEE 1588-2008 11.4.3. The equation in IEEE 1588-2008 11.4.3 doesn't include neighbor rate ratio correction. IEEE 1588-2008 6.5.5 offers neighbor rate ratio correction of link delay as a way to reduce residence time inaccuracy in peer-to-peer transparent clocks, but doesn't require it, and doesn't suggest such correction on ordinary clocks. On the other hand, the equation in IEEE Std 802.1AS-2020 16.4.3.2 includes neighbor rate ratio correction in the mean link delay calculation. IEEE Std 802.1AS-2020 seems to strongly suggest that all PTP instances should perform neighbor rate ratio correction, although 12.5.2.4.4 allows "other means" of computing mean link delay.

So in short, I believe ptpd disregards neighbor rate ratio because ptpd implements IEEE 1588-2008 PTPv2 and not IEEE Std 802.1AS-2020 gPTP.

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