2.2 7-Layer OSI Model
The open systems interconnection (OSI) model was the original standard description for how messages should be transmitted between any two points. To the five TCP/IP layers, OSI adds the following two layers:
- Layer 6, the session layer, which sets up and coordinates the applications at each end
- Layer 7, the presentation layer, which is the operating system part that converts incoming and outgoing data from one presentation format to another
The tasks of these two additional layers are dissolved into the application and transport layers in the newer five-layer model. The OSI model is becoming less popular. TCP/IP is gaining more attention, owing to its stability and its ability to offer a better communication performance. Therefore, this book focuses on the five-layer model.