Abstract: A system and method for controlling the transmission of frames or packets of data in a serial network which allows out-of-order delivery. The data frames transmitted by the initiator node to the recipient node include frame serial number or sequence count information. Acknowledgment frames, transmitted by the recipient node to indicate delivery of the data frame or packet, include matching serial number or sequence count information. According to one form of the present invention, the initiator node and recipient node include resources which relate the serial number or sequence count information, resources which include control information in the acknowledgment frame, and resources which determine the transmit status of all acknowledgment frames prior to that specified by serial number or sequence count in the acknowledgment frame.

Abstract: In a network communications system, data is transferred from a first node to a second node. When requested, the second node can transmit a data direction turnaround message to the first node, followed by transferring data to the first node. Data transfer in both directions is made during a single communications link within the network. The turnaround message can function as an acknowledgement of successful transfer to the data transferred from the first node to the second node.