You need to be able to have multiple nodes in one LAN access ports on each others’ containers without exposing those to the world and without using additional firewalls in front of the nodes.
That’s why kubernetes ended up removing docker support and instead recommends podman or using containerd natively.
In timekeeping, there are so called stratums to describe how correct a clock is.
Stratum 0 is a physical process, an inherent property of the universe. An atomic clock would be stratum 0.
Stratum 1 is a clock defined based on a stratum 0 clock. For example, GPS clocks are usually stratum 1, so are timeservers at universities with atomic clocks.
Stratum 2 is a clock defined based on a stratum 1 clock, for example, your router’s ntp server if it syncs its time based on gps or a university’s timeserver.
So if we adopt this jargon for units:
Meter is a stratum 1 unit, defined based on the stratum 0 properties of lightspeed and cesium resonance.
Inch is a stratum 2 unit, defined based on the stratum 1 meter.