Data Encapsulation

In computer networking, data encapsulation is the process of adding protocol headers and trailers to the original data as it moves through the network. The encapsulation process adds information to the data to ensure that it is transmitted and delivered properly to its destination.

Each layer of the networking protocol stack adds its own header and trailer to the data, forming a protocol data unit (PDU). When data is sent from an application on a source device, it is first encapsulated at the Application Layer with an application-specific header, such as the HTTP header for web traffic. The resulting PDU is then passed down to the lower layers of the stack for further encapsulation.

At the Transport Layer, the PDU is encapsulated with a Transport Layer header, such as the TCP or UDP header. The Transport Layer header includes information such as source and destination port numbers, sequence numbers, and acknowledgment numbers, which are used to ensure reliable end-to-end data delivery.

At the Internet Layer, the PDU is encapsulated with an Internet Protocol (IP) header. The IP header includes the source and destination IP addresses and other fields that help routers forward the data across the internet.

Finally, at the Network Access Layer, the PDU is encapsulated with a Layer 2 header and trailer specific to the network technology being used. For example, Ethernet uses a frame header and trailer that includes source and destination MAC addresses and a cyclic redundancy check (CRC) value for error detection.

When the data reaches the destination device, each layer of the protocol stack removes the corresponding header and trailer to extract the original data sent by the source device.