The invention relates to a method and a system for transmitting data packets between a terminal (1) and a network node (2) of a convergent communication network via a first channel (3) for a user service, wherein a switch to a second channel (5, 6, 7) is made if the transmission quality of the transmission decreases. The transmission is carried out in a continuous data stream, wherein a predetermined number of data packets per time unit is always present. In order to evaluate the transmission quality, the transmitted data are analyzed by an error detection unit (8) for errors and a switching unit (9) in the terminal (1) and/or in the network node (2) checks whether the number of errors at least within a transmission time window exceeds at least one predefined limit value. While maintaining the transmission of the predetermined number of data packets per time unit, the switching unit(s) (9) switch(es) to the second channel (4, 5, 7) when the at least one limit value is exceeded.