The Open Systems Interconnection (OSI) 7 Layer Model describes a mechanism for distinguishing functional areas of computer networking and how they relate to each other. 7 functional areas, or layers, describe how each particular layer relies on the layers below it but is relied upon by the layers above it. The OSI 7 Layer Model diagram contrasted with the TCP/IP 4 layer model is now available in the downloads section. The OSI 7 layer model forms the basis of most modern computer network communications technologies and is often compared with the more specific, and somewhat looser, TCP/IP layered model.