What does Macbeth tell Duncan about the duties of a king and his subjects?

The service and the loyalty I owe In doing it pays itself. Your highness' part Is to receive our duties, and our duties Are to your throne and state children and servants, Which do but what they should, by doing everything Safe toward your love and honor.  

Macbeth tells Duncan that his only duty as king is to accept what he's owed by his subjects, and that the duty of his subjects is the same as that of a child to its father or a servant to his master. He also adds that protecting the king is a part of his duty, it isn't commendable but natural.