What is Encapsulation
Encapsulation is the inclusion of one thing within another thing so that the included thing is not apparent. In networking, encapsulation is the process which includes one data structure within another data structure as a result that the first data structure hide for a limited time.
As application layer data passed down the protocol stack on its way for transmitting across the network media; various protocol pieces of information added at each level and the original data structure has changed. This is the encapsulation process.
What is De-encapsulation
De-encapsulation is the removal or the making clear a thing before encapsulated during the encapsulation process. This process has also reversed at the receiving host and is known as de-encapsulation. It is the process used by a receiving device to remove one or more of the protocol headers. The data de-encapsulated as it moves up the stack toward the end-user application.
Protocol Data Unit
The form that a piece of data takes at any layer called a protocol data unit (PDU). During encapsulation, each succeeding layer encapsulates the PDU; that it receives from the layer above by the protocol used. At each stage of the process; a PDU; has a different name to say its new functions. The PDUs has named according to the protocols of the TCP/IP suite, as shown below. Figure 2.3 Shows the protocol data unit(PDU) at different layers.
Data – The general term for the PDU used at the application layer and upper layers of the OSI Model.
Segment – This is the transport layer PDU.
Packet – This is the Network layer PDU.
Frame – This is Data Link layer PDU.
Bits – When physically transmitting data over the medium a physical layer PDU using.
Figure 2-3 PDU- PDUs at different layers