2.3. Introduction to Encapsulation
When a host transmits data across a network to another device, the data goes through encapsulation: It's wrapped with protocol information at each layer of the OSI model. Each layer communicates only with its peer layer on the receiving device.
To communicate and exchange information, each layer uses Protocol Data Units (PDUs). These hold the control information attached to the data at each layer of the model. They're usually attached to the header in front of the data field but can also be in the trailer, or end, of it.
At a transmitting device, the data-encapsulation method works like this:
User information is converted to data for transmission on the network.
Data is converted to segments, and a reliable ...
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