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TCP and UDP are the two transport-layer protocols. TCP trades speed for reliability; UDP trades reliability for speed. Knowing which services use each, and the TCP handshake, shows up across the SY0-701 networking objectives.
Last updated June 2026
| Aspect | TCP | UDP |
|---|---|---|
| Connection | Connection-oriented (three-way handshake) | Connectionless |
| Reliability | Reliable: guarantees delivery and order | Best-effort: no delivery guarantee |
| Ordering | Reassembles packets in order | No ordering |
| Overhead | Higher, slower | Lower, faster |
| Error handling | Acknowledgements and retransmission | None: lost packets are not resent |
| Header size | 20 bytes minimum | 8 bytes |
| Typical uses | HTTP/HTTPS, SMTP, SSH, file transfer | DNS, DHCP, VoIP, streaming, SNMP, TFTP |
TCP uses a handshake, acknowledgements, and ordering to guarantee delivery; UDP skips all of that for speed. Choose TCP when every byte must arrive intact, and UDP when speed matters more than the occasional lost packet.
Reading the difference is a start. SecPlus Mastery drills it with over 1,000 practice questions, timed mock exams, and spaced review across all five SY0-701 domains, so it sticks for exam day.
Written to the CompTIA Security+ SY0-701 objectives. CompTIA and Security+ are trademarks of CompTIA, used here for identification only.