What common cause leads to TCP segment retransmissions?

TCP segment retransmissions are primarily caused by network congestion that leads to packet loss. When packets are transmitted over a network and congestion occurs, some packets may become lost or dropped, preventing the receiving end from acknowledging their receipt.

In the context of TCP, when the sender does not receive an acknowledgment for a transmitted segment within a particular timeframe, it infers that the segment may not have reached the destination and subsequently retransmits the segment. This mechanism is a core part of TCP's reliability feature, ensuring that data is delivered accurately and in order.

While excessive bandwidth usage can contribute to network performance issues, it is not the primary reason for packet drops that lead to retransmissions. Low latency connections typically result in fewer retransmissions because faster response times reduce the likelihood of timeouts occurring due to missing acknowledgments. High QoS settings can improve packet delivery for prioritized traffic but do not inherently lead to retransmissions; instead, they aim to manage and optimize network resource usage effectively.

Thus, the correct identification of network congestion causing dropped packets as the common cause for TCP segment retransmissions highlights the fundamental behavior of TCP in managing reliable communication over potentially unreliable networks.