TCP/IP Model

The TCP/IP model is the set of communication protocols the internet actually runs on, organised into four layers. The Application layer contains protocols such as HTTP, DNS and SMTP; the Transport layer provides TCP and UDP; the Internet layer handles IP addressing and routing; and the Network Access (Link) layer moves data over physical media such as Ethernet and Wi-Fi.

Each layer adds its own header to the data on the way out and removes it on the way in, a process called encapsulation. The TCP/IP model is more practical and simpler than the seven-layer OSI model, which is mainly used for teaching and troubleshooting.