In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet Protocol Suite and the Open Systems Interconnection (OSI). The protocols of the layer provide host-to-host communication services for applications. It provides services such as connection-oriented data stream support, reliability, flow control, and multiplexing.

The best-known transport protocol of TCP/IP is the Transmission Control Protocol (TCP), used for connection-oriented transmissions, whereas the connectionless User Datagram Protocol (UDP) is used for simpler messaging transmissions.

UDP is a very simple protocol, and does not provide virtual circuits, nor reliable communication, delegating these functions to the application program. UDP packets are called datagrams, rather than segments. UDP may be used for multicasting and broadcasting, since retransmissions are not possible to a large amount of hosts and it typically gives higher throughput and shorter latency, and is therefore often used for real-time multimedia communication
TCP is the more complex protocol, due to its stateful design incorporating reliable transmission and data stream services. TCP is also used for HTTP web browsing and email transfer.