As
specified before, data streams from an application program or the OS, and
afterward goes down through the protocols and gadgets that make up the seven
layers of the OSI model, one by one, until the data lands at the physical layer
& is transmitted over the network link. The PC at the less than desirable
end inverts this procedure: The data comes in at the physical layer, goes up
through all the layers until it rises up out of the application layer, and is
made utilization of by the OS and any application programs.
At
every phase of the OSI model, the data is "wrapped" with new control
data identified with the work done at that specific layer, leaving the past
layers' data in place and wrapped inside the new control data. This control
data is diverse for every layer, except it incorporates headers, preambles,
trailers, and postambles.
For
instance, when data goes into the networking software and segments making up the
OSI model, it begins at the application layer and incorporates an application
header and application data (the real data being sent). Next, at the
presentation layer, a presentation header is wrapped around the data, and it is
gone to the part at the session layer, where a session header is wrapped around
the majority of the data, etc, until it achieves the physical layer. At the
accepting PC, this procedure is turned around, with every layer un-wrapping its
proper control data, performing whatever work is shown by that control data and
passing the data on to the following higher layer. Everything sounds rather
perplexing, yet it works exceptionally well practically speaking.
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