It's quite interesting - this isn't ethernet as we know it. Instead of each NIC using its own free-running clock, all the physical layers are sync'ed to each other at layer 1. (note that gigabit ethernet, which is what it uses, sends data at all times - when idle it sends the idle symbol)
P.S. There is WR workshop this week with some talks being publicly available on CERN's indico website.
Since cm precision is often not possible, is roundtrip-length an estimated average from prior roundtrips?
Sub-nanosecond synchronization is getting into the relativity is measurable realm.
In short, it's about giving PTP and SyncE some extra smarts.
Note that this is also for a large part a hardware-based technology
