Abstract: A facility is provided for use in a packet switch to control unnecessary multiple retransmissions of a data packet. In an exemplary embodiment of the invention, such control is achieved by tracking in a list the sequence numbers of transmitted data packets and retransmitting a data packet only if its sequence number appears in the list prior to the sequence number of the last data packet that is received correctly by a receiver. The sequence number associated with a retransmitted data packet is deleted from the list and then appended to the list to place the number in proper relationship with the sequence numbers of data packets transmitted after the initial transmission of the retransmitted data packet.

Abstract: A packet transmission protocol, which operates in a full-duplex mode in a system, which includes a transmitter, a receiver, and a communications network having a channel that logically ties the transmitter and the receiver together through the network, is disclosed. The receiver regularly sends a control packet to the transmitter. The control packet includes a plurality of data fields, which are useful in describing the state of the receiver to the transmitter. The transmitter receives the receiver's control packet and analyzes the data. If it finds that a particular block of packets had been received with an error (or not received at all), then the transmitter retransmits the block. The protocol includes two windows for controlling the volume of information, e.g. number of blocks, in the network.