Both TCP and UDP run on top of IP, but they make opposite architectural trade-offs to serve different networking needs. The rule of thumb in transport protocol selection is TCP for accuracy and UDP for timeliness.

When downloading a file or requesting a web page, accuracy is essential. TCP detects missing sequence numbers, holds transfer flow until retransmitting the exact lost packet, and adjusts its speed according to network conditions. While this ensures that no data is missing or out of sequence, the connection setup and retransmission logic make TCP slightly slower to start and potentially susceptible to delays.

In contrast, live media streaming and real-time communications prioritize low latency over complete reliability. Streaming systems using UDP trade away guaranteed delivery to avoid freezing playback over a dropped packet, often pairing with mechanisms like adaptive bitrate to lower video quality dynamically when bandwidth drops rather than stalling the stream.