I am fairly sure that traffic between nodes is not encrypted; I have dug into this in some detail with GCP staff. if you can quote some sources to the contrary

I am fairly sure that traffic between nodes is not encrypted; I have dug into this in some detail with GCP staff. if you can quote some sources to the contrary I'd be interested to see them. (The linked security design doc mentions 'encrypted in transit _to the data center_', but it doesn't address traffic inside the DC, last time I read through it in detail).