The transport layer forms the fourth layer in the OSI model, the standardized reference model for structuring network communication.
This layer is responsible for ensuring reliable communication between end devices in a network. The main tasks of the transport layer include segmenting data into smaller units, controlling the data flow, correcting errors and ensuring the sequence of the transmitted data. It therefore serves as a link between the transport-oriented and application-oriented layers. A logical end-to-end connection between the communicating systems takes place on this layer.
The transport layer uses standardized network protocols such as TCP (Transmission Control Protocol) or UDP (User Datagram Protocol). TCP ensures connection-oriented communication with confirmations and retransmission when required. UDP, on the other hand, offers simpler, connectionless communication without confirmations.