Sliding Window Protocols
Full duplex communication, i.e., same ckt is used to send data/ack in both directions.
Piggybacking: When data frame arrives, receiver (B) instead of sending an ack to A immediately, waits till it has a packet to send to (A) from its network layer. The ack is put in the frame header. Advantage: Better bandwidth utilization. Disadvantage: Waiting for packet could take for ever. Compromise wait a fixed time for packet to send otherwise send separate ack.