The majority of the protocols depicted in
the below illustration are called line ( link
or channel ) protocols or data link controls
(DLC). They are so named, because they control
the traffic flow between stations on one physical communication
& channel. Our goal in the remainder of
this topic is to provide a general description of
each of the protocols shown on the classification tree.
The data link protocols manage all communications traffic
on a channel. For example, if a communication port had
several users accessing it, the DLC would be responsible
for ensuring that all users had their data transported
error- free to the receiving node on the channel. The
DLC is generally unaware that the data
on the channel are from multiple users.
Data-link controls follow well-ordered steps in managing a communications channel:
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