Sequence Numbers (reminder How large do sequence numbers need to be? Must be able to detect wrap-around Depends on sender/receiver window size E.g Max seq=7, send win=recv win=7 If pkts 0. 6 are sent succesfully and all acks lost Receiver expects 7, 0.5, sender retransmits old 0.6! ! Max sequence must be s send window recv window Lecture 17: TCP Congestion Control4 Lecture 17: TCP & Congestion Control Sequence Numbers (reminder) • How large do sequence numbers need to be? • Must be able to detect wrap-around • Depends on sender/receiver window size • E.g. • Max seq = 7, send win=recv win=7 • If pkts 0..6 are sent succesfully and all acks lost • Receiver expects 7,0..5, sender retransmits old 0..6!!! • Max sequence must be  send window + recv window