TCP/IP
The fundamental protocol stack the entire internet is built on.
IP (Internet Protocol) handles addressing and packet splitting. TCP (Transmission Control Protocol) builds on top and guarantees packets arrive in the right order, without duplicates or losses — like a queue of cars where each car is labelled with an order number and missing cars are resent.
The alternative is UDP — faster but no guarantee packets arrive. Good for video streams, games, DNS — where a lost frame is less visible than a second of delay.