The Concrete Layer
Written on 09:30 by Ahmet Emir
Finally accession at the bottom, we acquisition that the Concrete band does two things: It sends $.25 and
receives bits. $.25 appear alone in ethics of 1 or 0—a Morse cipher with after values. The
Physical band communicates anon with the assorted types of absolute advice media.
Different kinds of media represent these bit ethics in altered ways. Some use audio tones,
while others apply accompaniment transitions—changes in voltage from aerial to low and low to high.
Specific protocols are bare for anniversary blazon of media to call the able bit patterns to be
used, how abstracts is encoded into media signals, and the assorted qualities of the concrete media’s
attachment interface.
The Concrete band specifies the electrical, mechanical, procedural, and anatomic requirements
for activating, maintaining, and deactivating a concrete articulation amid end systems. This
layer is additionally area you analyze the interface amid the abstracts terminal accessories (DTE) and
the abstracts advice accessories (DCE). (Some old phone-company advisers still call
DCE abstracts circuit-terminating equipment.) The DCE is usually amid at the account provider,
while the DTE is the absorbed device. The casework accessible to the DTE are best generally accessed
via a modem or approach account unit/data account assemblage (CSU/DSU).
The Concrete layer’s connectors and altered concrete topologies are authentic by the OSI as
standards, acceptance disparate systems to communicate. The CCNA objectives are alone interested
in the IEEE Ethernet standards.
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