Two latches agree to connect.
Why exchange three messages before sending data?
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Why exchange three messages before sending data?
Fit both endpoint latches and the clock.
The client’s SYN advertises its initial sequence. The server’s SYN-ACK acknowledges that SYN and advertises its own initial sequence. The final ACK acknowledges the server’s SYN. A lost reply leaves the handshake incomplete; retrying reuses the same SYN sequence number.
Ordered local TCP teaching model from RFC 9293. SYN consumes one sequence number. A lost SYN-ACK leaves the client in SYN-SENT; retransmitted SYN retains its original sequence number. Logical timeout is an illustrative control, not TCP’s adaptive RTO algorithm. No sockets, data transfer, simultaneous open or real network traffic.
Establish both endpoints with correct sequence acknowledgments after a lost reply.
Establish a connection despite a dropped SYN-ACK.