Transport Layer

The Transport Layer is Layer 4 of the OSI reference model and provides end-to-end communication between applications running on different devices. Its core functions include data segmentation, the identification of communication endpoints through port numbers and, depending on the protocol, flow and error control. TCP and UDP are among the most important transport protocols. TCP provides connection-oriented and reliable data transmission using acknowledgements, sequencing and retransmission of lost segments. UDP operates without establishing a connection and does not provide these mechanisms, resulting in lower protocol overhead. The Transport Layer is relevant to web applications, email, file transfers, streaming and many other network services. It provides the communication layer between the application-oriented OSI layers and the Network Layer.