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Encapsulation is a process to hide or protect a process from the possibility of outside interference or misuse of the system while simplifying the use of the system itself, also makes one type of network data packets to other data types. Encapsulation occurs when a protocol that is on the lower layer receives data from the protocol that is at a higher layer and put the data into a data format that is understood by the protocol. Access to the internal system so arranged through a set of interfaces.
With the encapsulation of data into an identity. A simple example encapsulation process in the process of mail delivery, if a letter would be sent but without the envelope, address and postage. The letter should have an identity in order to get to the destination, if it does not have an identity then the letter will not be able to get to the destination. Envelopes with address and stamp the same as the data encapsulation.
Encapsulation process varies in each layernya, the following process:

1. Initially the data was made, when starting the process of sending, the data fell through the application layer (layer 7)
responsible for the exchange of information from the computer to the network, basically this is an interface layer between network applications used by users. Can also be mentioned that this layer serves to define the request of the user. Then the data passed to the Presentation layer (layer 6), which layer is responsible for determining whether he needs to do the encryption on this request or to other forms of translational
data. If the process is complete, the next ditambahakan necessary information. Then forwarded to the session layer (layer 5) in which this layer will check whether an application requesting the information and verify that the services requested on the server. Any information will be passed down an added header of each layer. However, the processing layer 5, 6 and 7 sometimes it is not necessary to the header. This dikarena her no new information that needs to be processed.

2. Data arrived at the Transport layer (layer 4), ensuring that he already possessed a proper connection with the server and start the process by converting the information into the form of segments. Error checking and merging data coming from the same application done in this transport layer and the wholeness
data is guaranteed here as well. L4PDU formed from this process.

3. The next segment is forwarded to the Network layer (layer 3), here the segments received earlier and added the network address for the station to request and network address for the requested server. Segments will be converted into a packet-packet, then network layer makes
Network header, in which there are also addresses the network layer, and placed L4PDU behind it, and formed L3PDU.

4. Then the packet-packet was passed to the Data Link layer (layer 2) and the packages were arranged and then be wrapped again into the individual frames, one example of this process is to provide the MAC address of destination and source MAC address which is then used that information to make a trailer.
Because a packet can be delivered via many devices and routers, this is where the role of MAC addresses in packets sent between a router and other routers. Then be transmitted to the media. All
yanng information added by each layer before (as an actual file requests) must fit into a size of 46-1500 bytes of data fields in the ethernet frame. The data link layer is responsible for sending the frame according to the topology used. L2PDU formed in this process.

5. Finally, the data arrived at the Physical layer (layer 1), information will be taken from the source to the destination. Since the physical layer frame is not known, he would pass that information into the form of bits. The addition of the header does not occur at this layer. The Physical layer is associated with the hardware. Finally, the bits
They'll be synchronized and then converted into electrical signals in the form of high and low voltage and then transmitted through the media. Example of the cable to the destination, it is in accordance with the characteristics that determine the physical layer of a layer sequence of events in which the bit stream moving through a physical medium.
At each layer there is LxPDU (Layer N Protocol Data Unit), which is a form of bytes in the header-trailer on the data. PDU is the processes on each layer of the OSI model. At each layer is also formed a new formation, the layer 2 PDU including the header and trailer is called the frame formation. In the third layer is called packet (packet). While in layer 4 are called segments (segments).
After the encapsulation process, and then sent to the server and the server will perform this process in reverse, ie from the physical layer to application layer, this process is called decapsulation. If the encapsulation performed
packaging, then the decapsulation will perform the opening of the sheaths was through his layers.

Decapsulation process 
Decapsulation is the inverse of the encapsulation process. Encapsulation is the process of wrapping the data while the decapsulation process is a process of opening packs. The process was reversed from the encapsulation process. Encapsulation The process starts from the uppermost layer (Application Layer) to the lowest layer (Physical layer) while the decapsulation process starts from the lowest layer (Physical Layer) to the uppermost layer (Application Layer)