Data encapsulation (network technology)
The data encapsulation is understood to be the process in the OSI model and in the TCP / IP reference model , which supplements the data to be sent in the header (and possibly trailer) of the respective layers. In the OSI model, this affects the datagrams of layers 2 to 4, which are encapsulated (packaged).
Encapsulation process from layer 4 to 2 in the OSI model
From layers 7 to 5 only one data stream reaches layer 4. On the fourth layer, the data stream is broken down into data segments. This type of data encapsulation on the fourth layer is called segmentation . In addition, the data segment is addressed with a source and destination port number . After segmentation, the data segment is forwarded to the third layer.
On the third layer, the data segment of the fourth layer is encapsulated in a data packet of the third layer. This data packet is addressed with an IP address . What is now available is a data segment packed in a data packet. This is then forwarded to the second shift.
The second layer receives the data packet with the data segment contained therein as a datagram and encapsulates it (data packet) in a data frame . This data frame is given a MAC address and forwarded to layer 1, which converts the data frames into the physical and binary number system .
Decapsulation process from layer 2 to 4 in the OSI model
Layer 1 receives zeros and ones and uses them to form a data frame that is sent to layer 2. The log elements are removed there. What remains is a data packet that is sent to layer 3. There the layer 3 protocol elements are removed and the data segment then available is passed to layer 4. Layer 4 uses the port number to analyze to which service the content of the data segment is addressed. The data stream is then passed on to the higher layers.