How does TCP handle out-of-order packets?

TCP, or Transmission Control Protocol, is designed to ensure reliable data transfer across the network. One of its key features is its ability to maintain the order of packets, since data is often transmitted in segments over a network that may take diverse paths to reach the destination.

When it comes to out-of-order packets, TCP does not drop them; instead, it employs a systematic approach to handle them effectively. The correct answer highlights that TCP places segments with higher sequence numbers on hold while it waits for any missing segments that are needed to maintain the correct order. This is crucial for ensuring that the data is reassembled accurately for the application layer.

When TCP receives a packet that is not the expected next one (i.e., it has a higher sequence number than the last successfully received packet), it will hold onto that segment and not discard it. It uses a buffer to keep these out-of-order packets until the missing segment is received. This method allows TCP to ensure that the data stream is complete and in the correct sequence before delivering it to the application.

This functionality is part of what makes TCP a reliable transport layer protocol, as it guarantees data integrity and order, even if individual packets are delayed or arrive out of sequence during transmission.