This diagram illustrates the Open Systems Interconnection (OSI) model. OSI is primarily used today as a teaching tool. It conceptually devices a network into seven layers in a logical progression. The lower layers deal with electrical signals, chunks of binary data, and routing of these data across networks. Higher levels cover network requests and responses, representation of data, and network protocols as seen from a user's point of view. The OSI model was originally conceived as a standard architecture for building network systems and indeed, many popular network technologies today reflect the layered design of OSI.

Related References - OSI Model Tutorial
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