How do network layers interact in the OSI model?

Network layers in the OSI model interact by exchanging and interpreting data between adjacent layers through interfaces.

The Open Systems Interconnection (OSI) model is a conceptual framework that standardises the functions of a communication system into seven distinct categories, known as layers. These layers are, from top to bottom: Application, Presentation, Session, Transport, Network, Data Link, and Physical. Each layer provides a specific set of functions and communicates with the layers directly above and below it.

The interaction between these layers is facilitated by a process known as encapsulation. When data is sent from a source to a destination, it travels down the layers on the source side, across the network, and then up the layers on the destination side. At each layer on the source side, a header (and sometimes a footer) is added to the data packet. This process is reversed on the destination side, with each layer removing the corresponding header and footer.

For example, when an email is sent, the Application layer (Layer 7) begins the process by generating the data that needs to be transmitted. This data is then passed down to the Presentation layer (Layer 6), which converts the data into a standard format that can be understood by the receiving system. The Session layer (Layer 5) then establishes, manages, and terminates the connections between the two communicating systems.

The Transport layer (Layer 4) is responsible for end-to-end communication and error recovery. It divides the data into smaller packets and assigns sequence numbers to them. The Network layer (Layer 3) determines the best path for data transmission and handles logical addressing. The Data Link layer (Layer 2) frames the packets and checks for physical errors in the transmitted data. Finally, the Physical layer (Layer 1) transmits the binary data over the physical medium, such as a cable or wireless signal.

In summary, the layers in the OSI model interact by encapsulating data and adding their own specific information at each layer on the source side, and then de-encapsulating and interpreting this data at each layer on the destination side. This process ensures that data is correctly formatted, transmitted, received, and interpreted, regardless of the specific technologies and protocols used at each layer.