OSI Model
When two computers talk to each other, they need
to speak the same language.
The structure of this language is described in layers
by the OSI model.
The OSI model provides standards that allow
hardware, such as routers and
firewalls, to focus on one particular aspect of
communication that applies to
them and ignore others. The OSI model is broken
down into conceptual
layers of communica...
tion. This way, routing and firewall hardware can
focus
on passing data at the lower layers, ignoring the
higher layers of data encapsulation
used by running applications. The seven OSI layers
are as follows:
Physical layer This layer deals with the physical
connection between
two points. This is the lowest layer, whose primary
role is communicating
raw bit streams. This layer is also responsible for
activating, maintaining,
and deactivating these bit-stream communications.
Data-link layer This layer deals with actually
transferring data between
two points. In contrast with the physical layer,
which takes care of sending
the raw bits, this layer provides high-level
functions, such as error
correction and flow control. This layer also provides
procedures for activating,
maintaining, and deactivating data-link
connections.
Network layer This layer works as a middle ground;
its primary role is
to pass information between the lower and the
higher layers. It provides
addressing and routing.
Transport layer This layer provides transparent
transfer of data between
systems. By providing reliable data communication,
this layer allows the
higher layers to never worry about reliability or
cost-effectiven
transmission.
Session layer This layer is responsible for
establishing and maintaining
connections between network applications.
Presentation layer This layer is responsible for
presenting the data to
applications in a syntax or language they
understand. This allows for
things like encryption and data compression.
Application layer This layer is concerned with
keeping track of the
requirements of the applicatio
When two computers talk to each other, they need
to speak the same language.
The structure of this language is described in layers
by the OSI model.
The OSI model provides standards that allow
hardware, such as routers and
firewalls, to focus on one particular aspect of
communication that applies to
them and ignore others. The OSI model is broken
down into conceptual
layers of communica...
tion. This way, routing and firewall hardware can
focus
on passing data at the lower layers, ignoring the
higher layers of data encapsulation
used by running applications. The seven OSI layers
are as follows:
Physical layer This layer deals with the physical
connection between
two points. This is the lowest layer, whose primary
role is communicating
raw bit streams. This layer is also responsible for
activating, maintaining,
and deactivating these bit-stream communications.
Data-link layer This layer deals with actually
transferring data between
two points. In contrast with the physical layer,
which takes care of sending
the raw bits, this layer provides high-level
functions, such as error
correction and flow control. This layer also provides
procedures for activating,
maintaining, and deactivating data-link
connections.
Network layer This layer works as a middle ground;
its primary role is
to pass information between the lower and the
higher layers. It provides
addressing and routing.
Transport layer This layer provides transparent
transfer of data between
systems. By providing reliable data communication,
this layer allows the
higher layers to never worry about reliability or
cost-effectiven
transmission.
Session layer This layer is responsible for
establishing and maintaining
connections between network applications.
Presentation layer This layer is responsible for
presenting the data to
applications in a syntax or language they
understand. This allows for
things like encryption and data compression.
Application layer This layer is concerned with
keeping track of the
requirements of the applicatio
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