I wish there were a good alternative to master and slave that still had the connotation that the master did all the thinking and issued the orders, while the slave blindly obeyed. There are a fair number of protocols that work like that, and the alternatives I've seen don't capture that dynamic very well.

I've seen Parent and Child, but children definitely don't always do what the parent commands. I've seen Leader and Follower, but again, followers don't just blindly obey, they often let the leader take initiative, but they have some autonomy. Maybe Queen and Drone? I don't know enough about bees or ants to know if that's accurate though.