Layer 4: The Transport Layer

The Transport Layer is the basic layer at which one network computer communicates with another network computer. The Transport Layer is where you'll find one of the most popular networking protocols: TCP. The main purpose of the Transport Layer is to ensure that packets move over the network reliably and without errors. The Transport Layer does this by establishing connections between network devices, acknowledging the receipt of packets, and resending packets that aren't received or are corrupted when they arrive.

In many cases, the Transport Layer protocol divides large messages into smaller packets that can be sent over the network efficiently. The Transport Layer protocol reassembles the message on the receiving end, making sure that all packets contained in a single transmission are received and no data is lost.