- TCP is a connection-oriented protocol that establishes a full-duplex connection between two endpoints to deliver a byte stream in order with no message boundaries. - It uses sequence numbers and acknowledgments to ensure reliable and in-order delivery of all bytes. The sender will not overwhelm the receiver due to flow control. - TCP headers include source/destination ports, sequence numbers, acknowledgments, window size and checksum to establish connections, send data, and implement flow control and reliability.

1. Data Communication I Lecture 5 presented by Werner Wild, CEO Evolution Innsbruck, San Francisco, Zurich Contact: info@evolution.at

11. TCP ACK generation Event in-order segment arrival, no gaps, everything else already ACKed in-order segment arrival, no gaps, one delayed ACK pending out-of-order segment arrival higher-than-expect seq. # gap detected arrival of segment that partially or completely fills gap TCP Receiver action delayed ACK. Wait up to 500ms for next segment. If no next segment, send ACK immediately send single cumulative ACK send duplicate ACK, indicating seq. # of next expected byte immediate ACK if segment starts at lower end of gap

16. Receive Window (Example) application writes 2k sender receiver empty 4k 2k, seq=0 2k ack=2048, win=2048 application writes 3k 2k, seq=2048 4k full ack=4096, win=0 ack=4096, win=2048 2k application reads 2k 1k, seq=4096 2k 1k