How does the protocol work?
Does the node with the new entry send it to the other node all by itself? Or is there a table with the machines each node is responsible for updating?
I couldn’t find anything with regards to this info on the web.
Thanks 
Mnesia source code has some notes about implementation: otp/lib/mnesia/doc/misc at master · erlang/otp · GitHub
There’s an unofficial document with some diagrams concerning the replication protocol: Mnesia internals I guess you could call it a variation of 2-phase commit.