Final answer:
A TCP sender uses a very large retransmission timeout for the SYN segment to cope with the unpredictability of network conditions during the initial connection setup and to prevent unnecessary network traffic and potential confusion between the communicating parties.
Step-by-step explanation:
A TCP sender uses a very large retransmission timeout for the SYN segment to handle the uncertainty and delay in establishing a new connection. When a TCP connection starts, it begins with a three-way handshake process, where SYN and SYN-ACK messages are exchanged. This initial stage is crucial for setting up the parameters of the transmission, including the retransmission timeout value. Networks can be unpredictably slow, and the initial SYN message may take longer to be acknowledged due to several factors such as network congestion, routing paths, or the receiving host being busy with other tasks.
To avoid premature retransmissions, which could result in unnecessary network traffic and potential confusion between the sender and the receiver, a longer timeout is used for the SYN segment. The use of a larger initial timeout is a conservative approach to ensure that the connection setup is resilient to these varying network conditions. After the connection is established, the TCP stack can dynamically adjust the retransmission timeouts based on measured round-trip times.