CyberGuard dictionary / Network Security
User Datagram Protocol
User Datagram Protocol is a lightweight transport protocol that sends datagrams between application ports without guaranteeing delivery or ordering.
In simple terms
UDP sends messages with little built-in connection machinery. Applications that need reliability must provide it themselves or use another protocol.
Technical explanation
A UDP header carries source and destination ports, length, and checksum. The protocol does not establish a connection or retransmit missing datagrams; this can suit time-sensitive or request-response traffic.
UDP sends independent datagrams without built-in connection establishment, retransmission, or ordered delivery. Applications add reliability or security themselves when needed.
Examples in practice
A DNS resolver sends a small query using UDP and retries or uses another transport if it does not receive an adequate answer.
A real-time call prefers timely audio and can tolerate an occasional lost packet. A different UDP-based application implements its own acknowledgments because missing messages would be unacceptable.
Why it matters
UDP behavior matters when designing firewalls, troubleshooting loss, and choosing application-level safeguards.
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Sources and further reading
Published 2026-10-15 · Last updated 2026-10-15 · CyberGuard editorial content. Source links provide context; they do not imply endorsement.