In order that in a real-time capable Ethernet data network protocol the cycle time of the transmission cycles in a real-time capable Ethernet data network can be shortened, according to the invention a plurality of slaves (S1, S2, S3, S4, S5) is combined into a sum frame group (SG) and a slave (S2, S4) of the sum frame group (SG) is specified as collector node (SK) and all other slaves (S1, S2, S3, S4, S5) of the sum frame group (SK) transmit their data in each case with a collective data packet (DPS1, DPS2, DPS3, DPS4, DPS5) to the collector node (SK) transmit, the collector node (SK) inserts the data of the other slaves (S1, S2, S3, S4, S5) of the sum frame group (SG) into a sum frame data packet (DPSR) and the collector node (SK) transmits the sum frame data packet (DPSR) to the master (M).