The Open Systems Interconnection Model is a stack of protocols for system intercommunication. It is typically used mainly for abstract learning, as 7 layers is too cumbersome (it was made by comitee, go figure). ![[../../00 Asset Bank/Pasted image 20250902192605.png|invert_S]] - *Application*: - Most abstarct - Web pages, your app's source code, videos - *Presentation:* - Representation & Encryption (if not encrypted this is fairly useless) - *Session:* - A fairly useless layer that is for the station to create with a 'sesion-id' for some app, splits message into pieces - *Transport:* - Overlaps functionality, a session but with error checking things like checksums. - *Network:* - Nodes that don't share a physical link, but share a logical link - There is an *indirect* path from node $A\to B$ - This is where [[Packet-Switching]] happens. - *Data Link:* - Describes how two PHYSICALLY CONNECTED nodes communicate - Each 'node' needs its own identifier, *eg.* "address". - These organizes the set of 1's and 0's into individual 'frames' (another protocol) - *Physical*: - Least abstract - The physical electric currents, light pulses, opr radio waves conveying raw 1's and 0's Each layer is a set of promises - "heres what i can do, if you use me the right way."