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The OSI (Open Systems Interconnection) model, often referred to as the ISO / OSI layer model,
is a reference model used to describe and define communication between systems.
The reference model has seven individual layers, each with clearly defined tasks.
Essential features and tasks of the OSI model:
The reference model is composed of seven individual layers
In each shift, certain tasks are performed
individual layers are interchangeable
the communication between the layers is always hierarchical
with the layer directly below or above it
Interfaces define the exchange between the layers
The first four layers are transport-oriented
the layers 5 to 7 are application-oriented
The OSI layer model and its protocols
Protocols are defined in each layer of the reference model.
These protocols are compilations of rules for communication in the respective layer.
They are transparent to the protocols of the layers above or below them.
At the transitions of the layers, the protocols communicate via interfaces.
Some protocols perform multiple layer tasks and span two or more layers.
The seven layers of the OSI model
The following list shows the seven individual layers
of the OSI model and a brief description of their tasks:
Layer 1 - The physical layer or physical layer:
physical adaptation of the bits to the transmission medium
Layer 2 - The Data Link Layer or the Data Link Layer:
Segmentation of Data and Backup with Checksums
Layer 3 - The Network Layer or the Network Layer:
Switching the packets to the next network node
Layer 4 - The transport layer or the transport layer:
Allocation of data to the application
Layer 5 - The Session Layer or the Session Layer:
Control and Control of the Connection
Layer 6 - The Presentation Layer or the Presentation Layer:
Conversion of the data into independent formats
Layer 7 - The Application Layer or Application Layer:
Provide application functions such as data input and output
