7 layers that explain how computers talk to each other — made simple.
Click any layer to expand it
This is the top layer — the part you actually interact with! When you open a web browser, send an email, or use an app, you're using Layer 7. It's closest to you as a user.
This layer identifies communication partners, checks quality of service, handles user authentication, and defines the data format rules.
This layer is like a translator. It converts data into a format the other computer can understand, handles encryption (scrambling data to keep it secret), and compression (squishing data smaller).
Your operating system (like Windows or Mac) lives here. It ensures that information is reformatted back into the same format as the original on the receiving end.
This layer starts, manages, and ends conversations between computers. It establishes, coordinates, and terminates communications between applications on different devices.
When you're on a video call or downloading a file, the Session layer keeps the connection open and organized, then closes it properly when you're done.
This layer makes sure data arrives completely and in the right order. It handles end-to-end error recovery, flow control, and complete data transfer between systems.
It decides how much data to send at a time and checks that everything arrived. If something is lost, it knows to request it again.
This layer finds the best path for data across the world using IP addresses — like a home address for computers. Functions include routing, forwarding, addressing, and error handling.
Each piece of data gets labeled with source and destination IP addresses — like writing "From: your house, To: grandma's house" on a package.
Handles delivery between two directly connected devices using MAC addresses — a unique ID permanently burned into every network card. Unlike IP addresses, MAC addresses never change.
Wraps data into "frames" and checks for corruption. Has two sub-layers: MAC sub-layer (controls who sends data) and LLC sub-layer (error checking and flow control).
The bottom layer — the actual physical stuff. Cables, radio waves, electrical signals, and the hardware that sends and receives them. Everything becomes 1s and 0s (bits) sent through a physical medium.
When a network problem happens, technicians check here first — is the cable plugged in? Is the router powered on? Are the pins okay?
Data travels down when sending, up when receiving
What data is called at each layer
Silly sentences — the sillier, the stickier