What is the difference between the OSI model and the TCP/IP model. Is the OSI model the parent of the TCP/IP model?
A network layer model is simply a way of thinking about network protocols. It categorizes the features of a network protocol into layers that depend on the features of the lower layers. Thus it's useful to talk about the data link layer, which is responsible for moving the raw data, depending on the physical layer, which makes the network hardware accessible to upper layers.
The OSI model does not define specific protocols. It provides a model for designing network protocols that are strictly organized into layers. Protocols that reach across layers are frowned upon.
The TCP/IP model differs from the OSI model in three important ways:
- It defines fewer layers, with slightly different definitions, though the way OSI layers map to TCP/IP layers is pretty straightforward.
- TCP/IP does not demand strict layering. Cross-layer protocols are considered reasonable if they simplify implementation.
- Some core protocols are essential parts of the TCP/IP model. Indeed, the model named after two of them.
Here is a table of differences.