The transport layer has several protocols to transport data, including the following:
| Protocol | Purpose |
| TCP | Connection-oriented protocol that ensures reliable data transfer |
| UDP | Connectionless protocol used when speed, not reliability, is required |
| Stream Control Transmission Protocol (SCTP) | Reliably transmits data streams that have more than one IP address |
| Reliable User Datagram Protocol (RUDP) | Extends UDP by providing TCP-like qualities, such as flow control, acknowledgments, and re-transmitting lost packets |
Although there are other lesser-known transport layer protocols, we will discuss the two predominant protocols, TCP and UDP, starting with the more widely used protocol, TCP.