Piggybacking data transfer is a bit different from Sliding Window Protocol used in the OSI model. In the data frame itself, we incorporate one additional field for acknowledgment (called ACK).
Whenever party A wants to send data to party B, it will send the data along with this ACK field. Considering the sliding window here of size 8 bits, if A has received frames up to 5 correctly (from B), and wants to send frames starting from frame 3, it will send ACK6 with the data.
Three rules govern the piggybacking data transfer.
Advantages: Improves the efficiency
Disadvantages: The receiver can jam the service if he/she has nothing to send. This can be solved by enabling a counter (Receiver timeout) when a data frame is received. If the count ends and no data frames have been received, the receiver will send an ACK control frame. The sender also adds a counter (Emitter timeout), if the counter ends without receiving confirmation, the sender assumes packet loss, and sends the frame again.