checksum, seq. #, ACKs, retransmissions will be of help but not enough.
Suppose entire packet does not reach
sender set timeout.
retransmit if no ACK received in time.
if pkt / ACK just got delayed (not lost):
- retransmission will be duplicate, but seq handles this.
Lose packet We will timeout Resend packet
Corrupt packet Resend packet
Packet sent after timeout Seq no. is duplicated