Why it matters

Understanding UDP shapes app design for real-time and low-latency. It's not always the wrong choice; sometimes it's the right one.

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The architecture

Header: source port, dest port, length, checksum. That's it.

Datagrams: preserved boundaries. Sender sends N bytes, receiver gets N bytes (or nothing).

UDP characteristicsFixed 8-byte headerminimal overheadNo reliabilityapp must handleDatagram boundariespreservedApps often build reliability on UDP (QUIC, RTP) when needed selectively
UDP header + semantics.
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How it works end to end

Use cases: DNS (small query/response), video calls (drop stale frames), gaming (positions), DHCP, NTP.

Reliability layers: QUIC, RTP, custom protocols add selective reliability on top of UDP.

Firewalls: UDP more likely to be blocked than TCP; use TCP fallback if needed.