A method for adjusting a set of primary rate limits for transmission rates of data flows having a certain priority in a transmitter is provided. A mean value is determined of a duty cycle of the certain priority at the port as obtainable from the transmission or flow control, wherein the data flows having different priorities including said certain priority are transmitted by a port of the transmitter, transmissions for rate-limited data flows having the certain priority are limited by secondary rate limits (r1′, r2′, . . . rn′) per data flow, and transmissions for all data flows having the certain priority are controlled by a transmission or flow control per priority. The secondary rate limits (r1′, r2′, . . . rn′) are obtained by adjusting the primary rate limits for the transmission rates of the data flows having the certain priority based on the determined mean value of the duty cycle.