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The TCP/IP Guide  9  The Open System Interconnection (OSI) Reference Model

Comparing the OSI Reference Model to Network Architectures and Protocol Stacks 1 OSI Reference Model Networking Layers, Sublayers and Layer Groupings

The OSI Reference Model is valuable as a tool for explaining how networks function, and for describing the relationships between different networking technologies and protocols. To accomplish this, the model relies on a number of important concepts and terms. To understand the model, then, I need to explain what these are and how they relate to the model as a whole.

In this section, I describe the key concepts that define how the OSI Reference Model works. I begin with a discussion of how the model uses layers, perhaps the single most important model concepts. I then talk about some of the notation and jargon you are likely to see used in general discussions of the model. I define in more detail what “interfaces” and “protocols” are in the context of the model. I then explain the important concept of data encapsulation and the terminology used to refer to messages in the OSI Reference Model: PDUs and SDUs. Finally, I put together most of the preceding issues by describing how the various layers work to handle the routing of messages on a theoretical basis.

Comparing the OSI Reference Model to Network Architectures and Protocol Stacks 1 OSI Reference Model Networking Layers, Sublayers and Layer Groupings