[mlichvar]

Do the transparent clocks in your datacenter support unicast PTP?

There is a possibility to use PTP as a transport for NTP to take advantage of PTP-specific hardware timestamping. It could also process the correction field, but it seems the switches typically don't support unicast PTP.

The large asymmetry and banding of NTP in the test with Calnex Sentinel suggests it doesn't support the interleaved mode. NTP with hardware timestamping should normally be much more stable and symmetric, closer to PTP.

[throw0101a]

> but it seems the switches typically don't support unicast PTP.

Doing a quick search, the documentation for Cisco, Arista, and Juniper all mention unicast PTP, so it may be the feature is becoming more prevalent.

See also "Enterprise Profile for the Precision Time Protocol With Mixed Multicast and Unicast Messages":

* https://datatracker.ietf.org/doc/html/draft-ietf-tictoc-ptp-...

[mlichvar]

The unicast PTP support can be limited to boundary clocks and the enterprise profile doesn't require transparent clocks to support the unicast mode.

Also, there are different types of PTP transparent clocks. They can either be end-to-end or peer-to-peer, and either one-step or two-step clocks. To be useful for NTP, I think it would need to be an end-to-end transparent clock and ideally it would be a one-step clock to avoid dealing with with the follow-up messages.