OSI Reference Model: Application Layer Presentation Layer Sessions Layer Transport Layer Networks Layer Data Link Layer Physical Layer
At the end systems the first four layers act. The last three layers act in all the systems between the end systems. OSI is a communication model developed by ISO to regulate the of protocols between two systems when they interact. Each layer will have protocols to interact with the same layer on another machine. Also, each layer interacts with the next layer, and this interaction is termed as a service.