TCP: reliable data transfer event: data received from application above simplified sender, assuming create, send segment .one way data transfer no flow, congestion control wait event: timer timeout for fc segment with seq# y or event retransmit segment event: AcK received with ACK #y ACK processing 3: Transport Layer 3b-43: Transport Layer 3b-4 TCP: reliable data transfer simplified sender, assuming wait for event wait for event event: data received from application above event: timer timeout for segment with seq # y event: ACK received, with ACK # y create, send segment retransmit segment ACK processing •one way data transfer •no flow, congestion control