Rdt2.0: channel with bit errors
underlying channel may flip bits in packet
- recall: UDP checksum to detect bit errors
the question: how to recover from errors:
- acknowledgements (ACKs): receiver explicitly tells sender that pkt received OK
- negative acknowledgements (NAKs): receiver explicitly tells sender that pkt had errors
- sender retransmits pkt on receipt of NAK
- human scenarios using ACKs, NAKs?
new mechanisms in rdt2.0 (beyond rdt1.0):
- error detection
- receiver feedback: control msgs (ACK,NAK) rcvr->sender