We’ll describe OSI layers “top down” from the application layer that directly serves the end user, down to the physical layer. OSI was introduced in 1983 by representatives of the major computer and telecom companies, and was adopted by ISO as an international standard in 1984. However, the OSI 7-layer model is still widely used, as it helps visualize and communicate how networks operate, and helps isolate and troubleshoot networking problems. The modern Internet is not based on OSI, but on the simpler TCP/IP model. It was the first standard model for network communications, adopted by all major computer and telecommunication companies in the early 1980s The Open Systems Interconnection (OSI) model describes seven layers that computer systems use to communicate over a network.
