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OSI
Layers Model
Data
Link Layer
The next layer is the data link layer. This is the layer
that actually constructs the frames, and it also performs
error checking using CRC.
It ensures that the frames are
sent up to the next layer in the same order that they were
received, providing an error free virtual path to the
network layer. The data link layer consists of two sub
layers; the logical link control (LLC) and the media access
control (MAC), which provide reliable communications by
ensuring the data link is not broken and also by examining
packet address information. A bridge is an example of a
device that works at this layer. A bridge learns, forwards
and filters traffic by examining the layer 2 MAC address.
This helps segment network traffic. More recently, bridges
have been replaced by switches, which performs the same
functions as a bridge, but can do so on each port. To find
out more about switches, visit the Products link on the
left.
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