- Transport Layer
- The Transport Layer is the layer that is responsible for transmitting data between two endpoints utilizing a virtual multiplexed connection with virtual port numbers indicating the communication endpoints.
Since we're talking about the TCP/IP model, we're really talking about Transmission Control Protocol and User Datagram Protocol at this layer. Both protocols are responsible for transferring data between two endpoints (computers) running Internet Protocol. The idea of endpoints is critical. The transport layer handles end-to-end communication, not all the hops in-between.
UDP is categorized as a unreliable protocol. does not perform any connection setup or teardown and does not verify that the data got there in one piece. UDP relies on the Application to manage retransmission of lost data.
TCP is called a reliable protocol for transmitting data. TCP not only sets up the connection, negotiates the communication parameters, but also verifies that the data got to the destination machine intact. The destination machine can use TCP to request retransmission of lost or damaged frames.