Referring to the protocol or protocols operating at a particular level within a network architecture. Such an architecture commonly is detailed in a protocol stack, such as the OSI Reference Model, or protocol suite, such as the TCP/IP protocol suite.The OSI Reference Model is a full seven-layer stack, of which the top layer, the Application Layer, addresses applications and end user processes.The bottom layer, the Physical Layer, deals with physical and mechanical aspects of the interface between a device and a transmission medium. Although each layer addresses different functions and responsibilities, the layers work together, as a whole, to enable an application or end user process. See also application, Application Layer, OSI Reference Model, Physical Layer, protocol, and TCP/IP.