What can cause TCP segments to arrive out of order?

TCP segments can arrive out of order due to variations in routing paths. This occurs because TCP is built on top of an IP network, where packets may take different paths through the network to reach the destination. The decision on which path to take can be influenced by several factors, such as varying traffic loads, changes in network topology, or the configuration of routers along the way.

When segments are sent simultaneously or in rapid succession, they might traverse different routes that have varying latencies or speeds, leading them to arrive at their destination in a sequence that differs from the order in which they were sent. TCP has mechanisms to reorder these segments upon receipt to ensure that they can be processed correctly, but the underlying cause of the out-of-order delivery is indeed the dynamic nature of the routing paths they take across the network.

While defective network hardware and inadequate bandwidth allocation can lead to packet loss or delays, they do not inherently cause packets to arrive out of order in the same way that variations in routing paths do. Password protection has no relevance to the ordering of TCP segments.