[delayclose2]

> The offset is practically 0 ranging within nanoseconds range.

Uhm, no, the graph clearly shows that the offset is varying between 0-2 microseconds, which is 0 - 2,000 nanoseconds.

2,000 nanoseconds is not "practically zero". PTP precision is supposed to be in the 10ns range.

Also, how did they get 40us precision on (what I assume to be) a normal kernel on a normal x86 box? I would have assumed that in a datacenter environment, with traffic levels being random, the jitter introduced in the kernel networking stack alone would be in the hundreds of microseconds at least.

[michaelt]

PTP is a standard feature on a lot of Intel chipsets so a lot of servers have it 'for free' and aren't using it.

It timestamps packets at the network card - independently of any kernel timing.

[zinekeller]

Addenda: Intel networking chips, so even in AMD or ARM systems this actually works (assuming that you have the correct OS and drivers/modules/support software).

Also, this isn't exclusive to Intel: most modern (server) NICs at least support TCXO-based timings, and some built for precision uses OCXO for even better precision.