This document describes the encapsulation and decapsulation process as a message passes through the layers of the OSI model. As the message moves from the physical layer at the source to the application layer at the destination, each higher layer encapsulates the message from the layer below and adds its own header. During decapsulation at the destination, headers are removed in reverse order as the message moves down the layers.

1. Encapsulation/Decapsulation
Physical
Data Link
Network
Transport
Application
Source
Router
Message
Message
Message
Message
4
4
4
3
3
2
Physical
Data Link
Network
Transport
Application
Destination
Message
Message
Message
Message
4
4
4
3
3
2
Message
Message
4
4
3
3
2
1 Message
4
3
2 1 Message
4
3
2 1 Message
4
3
2
- the process of adding/removing control information
as a message passes through the layered model