A switch (1) for the transfer of data packets comprises in the conventional way input ports (3) and output ports (5) and parallel switching planes, which are identical to each other. The switch (1) establishes connections between input ports (3) and output ports (5) through the parallel switching planes. In each output port (5) there is for each switching plane and each established connection a buffer (25) accommodating at least one data packet. In the output port there is in addition a logical selection device (29) for selecting data packets from the switch (1) and from the different planes in such a way that a data packet stream, which is as correct as possible, is obtained from the output port, and it selects in the first place data packets from a switching plane, which is the preferred plane at each instant. The selection device (29) comprises a quality determining unit, which at each occasion determines the preferred plane by means of quality values for each plane. These quality values are determined by means of an evaluation of data packets, which have arrived earlier to the output port.