Packet switch and switching method for switching variable length packets

A packet switch for switching variable length packets, where each output port interface includes a buffer memory for storing transmission packets, a transmission priority controller for classifying, based on a predetermined algorithm, transmission packets passed from a packet switching unit into a plurality of queue groups to which individual bandwidths are assigned respectively, and queuing the transmission packets in the buffer memory so as to form a plurality of queues according to transmission priority in each of the queue groups and a packet read-out controller for reading out the transmission packets from each of the queue groups in the buffer memory according to the order of transmission priority of the packets while guaranteeing the bandwidth assigned to the queue group.