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[RE] Reference to the crystal clock accuracy

As I mentioned on telco, ax excerpt about crystal clock accuracy from Stefano Bregni, Synchronization in Digital Communication Networks, p 209, last sentence in the section 5.3.2 "Accuracy".

"Quartz-oscillators can be very stable in the short term, but they drift in frequency and do not feature the frequency accuracy of atomic clocks. [5.9]"

Something to keep in mind though : clocks derived from the Crystal oscillators can be deliberately added with jitter to meet the emission standard requirements. This essentially spreads generated emission power over a larger frequency range. But I believe that this jitter is less considerable then the one we get when transmitting timestamps over the Ethernet.