A
networking protocol using all or some of the layers listed in the OSI reference model move
data between devices. Recall that Layer 7 is the part of the protocol that communicates with
the application, and Layer 1 is the part of a protocol that communicates with the media. A
data frame is able to travel across a computer network because of the layers of the protocol.
The process of moving data from one device in a network is accomplished by passing
information from applications down the protocol stack, adding an appropriate header at
each layer of the model. This method of passing data down the stack and adding headers
and trailers is called encapsulation. After the data is encapsulated and passed across the
network, the receiving device removes the information added, using the messages in the
header as directions as to how to pass the data up the stack to the appropriate application.
Data encapsulation is an important concept to networks. It is the function of like layers on
each device, called peer layers, to communicate critical parameters such as addressing and
control information.
Although encapsulation seems like an abstract concept, it is actually quite simple. Imagine
that you want to send a coffee mug to a friend in another city.
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