OSI Reference Model with example

Example: Saying "Hello" in a message User Action: On Computer A, a user types "hello" into a messaging software and sends it to Computer B. 

Application Layer: Computer A's messaging programs starts the request to send the "hello" message.

Presentation Layer: The message is ready to be sent, and it might be encoded for compatibility or security reasons. 

Session Layer: Computers A and B establish a session between their messaging programs

Transport Layer: TCP guarantees reliable transmission of the "hello" message by breaking it up into packets. 

Network Layer: To route packets between Computer A and Computer B via the network, IP addresses are added. 

Data Link Layer: To transmit data between Computer A and the local network's devices, MAC addresses are appended to frames.

Physical Layer: Using fibre optics or Ethernet cables, the "hello" message frames are sent as light pulses or electrical impulses.

The message travels through the physical, data link, network, transport, session, presentation, and application layers in the opposite order at Computer B, which is the receiving end of the process. This is done until Computer B's messaging application displays the "hello" message, concluding the communication between the two computers.