D-Link DES-3326SR User Manual page 82

DES-3326SR Layer 3 Fast Ethernet Switch User's Guide
layers communicate by an internal interface. This interface is
usually not publicly documented and is frequently proprietary.
It has some of the same characteristics of a protocol and two
stacks from the same software vendor may communicate in the
same way. Two stacks from different software vendors (or
different products from the same vendor) may communicate in
completely different ways. As long as peers can communicate
and interoperate, this has no impact on the functioning of the
network.
The communication between layers within a given protocol
stack can be both different from a second stack and
proprietary, but communication between peers on the same
OSI layer is open and consistent.
A brief description of the most commonly used functional
layers is helpful to understand the scope of how protocol
layering works.
Layer 1
This is referred to as the physical layer. It handles the
electrical connections and signaling required to make a
physical link from one point in the network to another. It is on
this layer that the unique Media Access Control (MAC) address
is defined.
Layer 2
This layer, commonly called the switching layer, allows end
station addressing and the establishment of connections
between them.
Layer 2 switching forwards packets based on the unique MAC
address of each end station and offers high-performance,
dedicated-bandwidth of Fast or Gigibit Ethernet within the
network.
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