The most popular packet-based structure of layers, or protocol stack, is called the OSI model (Open System Interconnection) which was created, oddly enough by the reverse acronymn, the ISO (International Organization for Standardization). It defines 7 layers. The user interface (Application Layer) is the top layer, since users work directly with applications. As you work your way down toward the lower layers, the protocols become more detailed toward the nuts and bolts of the operation. They define the details of actually preparing and moving data.
Although there is officially no layer 0 or 8 – conceptually they exist as the physical link (the cable) and the User, as shown below. Note how the packets get larger as each successive layer adds it’s own header to the packet that was handed down to it from the layer above.
Although there is officially no layer 0 or 8 – conceptually they exist as the physical link (the cable) and the User, as shown below. Note how the packets get larger as each successive layer adds it’s own header to the packet that was handed down to it from the layer above.
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