What is the encapsulation process for each layer in the OSI model?

In the OSI model, encapsulation occurs as data is passed down through the layers. At the Application layer (Layer 7), data is created and then passed to the Presentation layer (Layer 6) for formatting. The Session layer (Layer 5) manages sessions, while the Transport layer (Layer 4) adds headers for segmentation and reliability. As data moves down to the Network layer (Layer 3), it receives IP addressing, followed by the Data Link layer (Layer 2), which adds MAC addressing and framing, and finally, the Physical layer (Layer 1) transmits the raw bits over the physical medium. Each layer adds its own header (and sometimes footer) to the data, forming a protocol data unit (PDU) specific to that layer.