A method of processing a data unit of a first protocol layer for transmission in a data unit based communication system is described, comprising the steps of passing to a second protocol layer a given data unit of said first protocol layer that is to be transmitted, determining a numeric value of a numerically quantifiable parameter associated with said given data unit of said first protocol layer, embedding said given data unit of said first protocol layer into one or more data units of said second protocol layer, performing transmission control for said one or more data units of said second protocol layer in accordance with said numeric value of said numerically quantifiable parameter.