UDP doesn't guarantee delivery, doesn't retry failures, doesn't even care if your packets arrive. For video calls and online games, that's exactly what makes it work.
TCP's reliability becomes a liability when late data is worse than lost data. Real-time applications need UDP precisely because it doesn't try to help.
TCP treats every lost packet as a crisis. UDP asks a different question: does this data still matter? Here's how to detect loss, recover selectively, prevent it with redundancy, or fake it entirely with prediction.
Why does a 'reliable' protocol make real-time worse? Because in gaming, VoIP, and streaming, old data isn't late—it's wrong. UDP lets applications be smart about what to lose.
Neither device can reach the other first—so both reach out simultaneously. The packets get rejected, but rejection itself creates the openings they need.
TCP's reliability comes packaged with constraints designed in 1974. QUIC delivers the same guarantees—encrypted connections, ordered delivery, loss recovery—without the handshake rituals, the head-of-line blocking, or the fragile identity that breaks when you switch networks.
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