TCP

A reliable transport protocol that provides ordered byte streams between networked applications.

Motivation

TCP solves the problem of sending data reliably across unreliable networks. Packets can be dropped, duplicated, delayed, or reordered; TCP hides much of that complexity from applications.

Where it fits

TCP belongs to computer networks and supports protocols such as HTTP, HTTPS, and many database/client-server connections.

Mental model

TCP creates a reliable byte stream between two endpoints. It uses acknowledgements, retransmission, ordering, and flow control to make network communication more dependable.

Common mistakes

Thinking TCP sends messages instead of a byte stream.
Forgetting that TCP reliability does not mean application-level success.
Assuming TCP is always better than UDP.