The method comprises the steps of: a) providing a plurality of memory buffers, associated to respective indexes of priority, each buffer comprising one queue of frames having a same index of priority, b) sorting the received frames in a chosen buffer according to their index of priority, c) in each buffer, sorting the frames according to their respective timestamps, for ordering the queue of frames in each buffer from the earliest received frame on top of the queue to the latest received frame at the bottom of the queue, and d) feeding the transmitting ports with each frame or block of frame to transmit, in an order determined according to the index of priority of the frame, as well as an order of the frame or of the block of frame in the queue associated to the index of priority of the frame.