D-Link DES-3326 User Manual page 100

24-port NWay Ethernet Switch User's Guide
Figure 5-10. 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
84 Switch Management and Operating Concepts