Abstract: A switch for the transfer of data packets comprises in the conventional way input ports and output ports and parallel switching planes, which are identical to each other. The switch establishes connections between input ports and output ports through the parallel switching planes. In each output port there is for each switching plane and each established connection a buffer accommodating at least one data packet. In the output port there is in addition a logical selection device for selecting data packets from the switch 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 comprises a quality determining unit, which at each occasion determines the preferred plane by means of quality values for each plane.

Abstract: To provide a correct outgoing stream of data packets for each established connection (having identifying number vc/vp) in a data packet switch, which comprises several parallel switching planes, which are identical to each other, there is for each output port for each switching plane and each established connection a buffer arranged to store at least one data packet. When a first data packet arrives to an output port it is immediately tested by a control device for this output port, if this first data packet is the next data packet, which is in turn to be forwarded from the switch. In a first case, when this condition is satisfied, the data packet is forwarded from the switch. In a second case, when this condition is not satisfied, the data packet is stored in the buffer, which is arranged for the connection, to which said data packet belongs, and for the switching plane, through which the data packet has travelled.