Abstract: In a data communication system, a sending entity divides data into a plurality of groups, each of which is segmented into a plurality of packets, and then sequentially transmits the packets in each group to the receiving entity. The receiving entity receives each packet, and determines whether the packet is sequentially received in a group. When an out-of-sequence error arises, the receiving entity discards the received packet, and sends a negative acknowledgment to the sending entity if no negative acknowledgment has been sent for the group. Only a single negative acknowledgment is sent for the group until an expected packet is received. When all packets of the group are received, the receiving entity sends a positive acknowledgment to the sending entity.

Abstract: A novel system and apparatus for transmitting data between the two nodes of a network is provided. The transmission is effected by using an error recovery protocol featuring a positive group acknowledgement. A sender unit on one node receives the user data and groups the data into consecutive cells, the cells being clustered into groups, each cell in a group being assigned a unique sequence number. The groups of cells are transmitted over a physical channel to a receiver unit on a different node. The receiver unit examines the cell stream and issues an acknowledgment message to the sender unit only when all of the cells in a group have been received. Once the sender unit has completed the transmission of a group of cells, it starts observing the physical channel for an acknowledgement message from the receiver unit. If after a predetermined time period the acknowledgement message has not been received, the sender unit transmits the group of cells again.