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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)
Not on GitHub?
In short, it's about giving PTP and SyncE some extra smarts.
Haven't looked into this in depth but sub-nanosecond sync for systems up to 10km apart is interesting since 10km is about 33 light microseconds. There is some trickery going on.
Two-way time transfer measures the round-trip propagation time. As a result, it's not directly relevant to the accuracy.
Since cm precision is often not possible, is roundtrip-length an estimated average from prior roundtrips?
Earlier quoted context omitted.
Two-way time transfer measures the round-trip propagation time. As a result, it's not directly relevant to the accuracy.
So then you need to know distance / roundtrip-length within centimeter precision as well (below 29.98 cm for sub-nanosecond precision… to be precise). Since cm precision is often not possible, is roundtrip-length an estimated average from prior roundtrips?
jitter kills
Earlier quoted context omitted.
Two-way time transfer measures the round-trip propagation time. As a result, it's not directly relevant to the accuracy.
So then you need to know distance / roundtrip-length within centimeter precision as well (below 29.98 cm for sub-nanosecond precision… to be precise). Since cm precision is often not possible, is roundtrip-length an estimated average from prior roundtrips?
Haven't looked into this in depth but sub-nanosecond sync for systems up to 10km apart is interesting since 10km is about 33 light microseconds. There is some trickery going on.
Yes, it uses phased locked loops and measures phase difference between the master clock and the local clock.
Some may find https://gitlab.com/ohwr/project/white-rabbit/-/wikis/home an easier starting point. Particularly the "Synchronization" page. In short, it's about giving PTP and SyncE some extra smarts.
Haven't looked into this in depth but sub-nanosecond sync for systems up to 10km apart is interesting since 10km is about 33 light microseconds. There is some trickery going on.
Not on GitHub?
Its on gitlab but even there I failed to find sources, documentation/presentations are there though
Note that this is also for a large part a hardware-based technology