Connectionless, unreliable transport protocol providing fast, best-effort delivery for real-time applications. Essential knowledge for network engineering and communication systems design.
No handshaking or connection establishment. Each datagram is independent, allowing minimal latency overhead—ideal for real-time streaming and gaming.
No acknowledgments, retransmissions, or sequencing guarantees. Applications must handle loss, duplication, and ordering if required.
8-byte fixed header vs TCP's 20-60 bytes. Maximizes payload efficiency for high-throughput applications like video streaming and VoIP.
Interactive breakdown of the 8-byte UDP header. Hover over fields to see detailed specifications.
App passes data to UDP with destination IP and port.
UDP adds 8-byte header with source port, length, and checksum.
Datagram handed to IP layer with protocol field = 17 (0x11).
IP routes packet; no delivery guarantees from UDP.
Includes IP header fields for additional integrity verification:
| Feature | UDP | TCP |
|---|---|---|
| Connection | Connectionless | Connection-oriented (3-way handshake) |
| Reliability | Best-effort, no guarantees | Acks, retransmissions, sequencing |
| Ordering | No ordering guarantees | In-order delivery guaranteed |
| Header Size | 8 bytes (fixed) | 20-60 bytes (variable) |
| Speed | Fast (low latency) | Slower (congestion control) |
| Flow Control | None | Sliding window mechanism |
| Congestion Control | None | Slow start, congestion avoidance |
| Use Cases | DNS, VoIP, Gaming, Streaming | HTTP, FTP, Email, File Transfer |
Domain Name System queries use UDP port 53 for fast lookups. Falls back to TCP for large responses (>512 bytes).
Real-time Transport Protocol carries voice/video over UDP. Tolerates packet loss better than delay.
Fast-paced games use UDP for position updates. Custom reliability layers built on top for critical data.
Modern web protocol built on UDP. Combines speed with TLS encryption and multiplexed streams.