Protocol Master is a title used on the planet Kostolain referring to an individual assigned to oversee the proceedings of ceremonies and rites. Kostolain culture is exceedingly reserved and formal, with a strong need to follow the strict letter of the law regarding all ceremonies. The Protocol Master ensures that "priorities" are observed at every step of the proceedings and that strict protocol is practiced at each stage.
Erko served as Protocol Master for the planned wedding of Campio and Lwaxana Troi in 2368. (TNG: "Cost of Living")