D-Link DES-3250TG User Manual page 56

DES-3250TG Layer 2 Fast Ethernet Switch User's Guide
Figure 5- 6. OSI Seven Layer Network Model
Each layer is a distinct set of programs executing a distinct set
of protocols designed to accomplish some necessary tasks.
They are separated from the other layers within the same
system or network, but must communicate and interoperate.
This requires very well defined and well-known methods for
transferring messages and data. This is accomplished through
the protocol stack.
Protocol layering as simply a tool for visualizing the
organization of the necessary software and hardware in a
network. In this view, Layer 2 represents switching and Layer 3
represents routing. Protocol layering is actually a set of
guidelines used in writing programs and designing hardware
that delegate network functions and allow the layers to
communicate. How these layers communicate within a stack
(for example, within a given computer) is left to the operating
system programmers.
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