TCP/IP Data Encapsulation and Decapsulation

This lesson will teach you what is TCP/IP encapsulation and decapsulation, and how data is packed at different layers of TCP/IP protocol suit.

Encapsulation

When data moves from upper layer to lower level of TCP/IP protocol stack (outgoing transmission) each layer includes a bundle of relevant information called a header along with the actual data. The data package containing the header and the data from the upper layer then becomes the data that is repackaged at the next lower level with lower layer's header. Header is the supplemental data placed at the beginning of a block of data when it is transmitted. This supplemental data is used at the receiving side to extract the data from the encapsulated data packet. This packing of data at each layer is known as data encapsulation.

TCP IP Encapsulation

TCP/IP Encapsulation

Decapsulation

The reverse process of encapsulation (or decapsulation) occurs when data is received on the destination computer. As the data moves up from the lower layer to the upper layer of TCP/IP protocol stack (incoming transmission), each layer unpacks the corresponding header and uses the information contained in the header to deliver the packet to the exact network application waiting for the data.

TCP IP Decapsulation

TCP/IP Decapsulation

The format of the data packet generated at different layers is different, and known by different names.

The data packet created at the Application layer is known as a "MESSAGE".

As described in the previous lesson, the Transport Layer contains two important protocols: TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). TCP is more reliable but consumes more resource. UDP is less reliable but consume fewer resources than TCP and is faster than TCP.

The Application layer message is again encapsulated at the Transport layer. If the protocol used at the Transport Layer is TCP, the data packet is known as a "SEGMENT". If the protocol used at the Transport layer is UDP, the data packet is known as a "UDP DATAGRAM".

The data packet created at the Internet layer by Internet Protocol, which again encapsulates the Transport layer segment/datagram, is known as a "IP DATAGRAM".

The data packet at the Network Access layer, which encapsulates and may subdivide the datagram, is known as a "FRAME". The frame is converted into a bitstream at the lowest sublayer of the Network Access layer and then placed on medium.

In this lesson, you have learned what is TCP/IP Encapsulation and Decapsulation. The name of Data at different layers of TCP/IP protocol stack are Message, TCP Segment, UDP Datagram, IP Datagram and Frame.