TCP is a connection-oriented protocol, whereas UDP is a connectionless protocol. A key difference between TCP and UDP is speed, as TCP is comparatively slower than UDP. Overall, UDP is a much faster, simpler, and efficient protocol, however, retransmission of lost data packets is only possible with TCP.
| Basis | Transmission control protocol (TCP) | User datagram protocol (UDP)
| Type of Service | TCP is a connection-oriented protocol. Connection-orientation means that the communicating devices should establish a connection before transmitting data and should close the connection after transmitting the data. | UDP is the Datagram-oriented protocol. This is because there is no overhead for opening a connection, maintaining a connection, and terminating a connection. UDP is efficient for broadcast and multicast types of network transmission. |
| Reliability | TCP is reliable as it guarantees the delivery of data to the destination router. | The delivery of data to the destination cannot be guaranteed in UDP. |
| Error checking mechanism | TCP provides extensive error-checking mechanisms. It is because it provides flow control and acknowledgment of data. | UDP has only the basic error checking mechanism using checksums. |
| Acknowledgment | An acknowledgment segment is present. | No acknowledgment segment. |
| Sequence | Sequencing of data is a feature of Transmission Control Protocol (TCP). this means that packets arrive in order at the receiver. | There is no sequencing of data in UDP. If the order is required, it has to be managed by the application layer. |
| Speed | TCP is comparatively slower than UDP. | UDP is faster, simpler, and more efficient than TCP. |
| Retransmission | Retransmission of lost packets is possible in TCP, but not in UDP. | There is no retransmission of lost packets in the User Datagram Protocol (UDP). |
| Header Length | TCP has a (20-60) bytes variable length header. | UDP has an 8 bytes fixed-length header. |
| Weight | TCP is heavy-weight. | UDP is lightweight. |
| Handshaking Techniques | Uses handshakes such as SYN, ACK, SYN-ACK | It’s a connectionless protocol i.e. No handshake |
| Broadcasting | TCP doesn’t support Broadcasting. | UDP supports Broadcasting. |
| Protocols | TCP is used by HTTP, HTTPs, FTP, SMTP and Telnet. | UDP is used by DNS, DHCP, TFTP, SNMP, RIP, and VoIP. |
| Stream Type | The TCP connection is a byte stream. | UDP connection is message stream. |
| Overhead | Low but higher than UDP. | Very low. |