title: What is cross-timestamp?
body: <p>My linux system is using linuxptp for network time-sync. I am doing research to see if my system clock can be disciplined to the accuracy at nanosecond level. I ran into this document talking about "cross timestamp" and I don't quite understand what it does and if it can help sync my system clock to the accuracy of nano-second level.
  <a href="https://lore.kernel.org/patchwork/patch/654619/" rel="nofollow noreferrer">https://lore.kernel.org/patchwork/patch/654619/</a>
  I'd appreciate your insights</p>