backup encryption key

Dear community,

I have some questions around the backup encryption key:

- What is the AES operation mode (e.g. CBC, GCM, CTR, etc.)?
- what is the key hierarchy. I assume that eventually, the Unit Key will protect all other keys, but do we then only have the master key protecting the SSL private keys or are there more levels?
- How is the master key being shared between F5 units?
- How is the unit key being stored and encrypted?