Bottoms Up Model
A bottoms-up, layered model is the canonical approach network design overall. This model is known as the Open Systems Interconnection model ("OSI") and is a useful model for problem solving, particularly when used in conjunction with the inside-out model.
The OSI model is has 7 layers, from bottom to top:
| Level # | Name | Examples |
|---|---|---|
| 7 | Application | the Facebook mobile app |
| 6 | Presentation | Data formats like ASCII (and de/encoding as such) |
| 5 | Session | PPTP (a protocol used to create Virtual Private Networks) |
| 4 | Transport | |
| 3 | Network | |
| 2 | Data link | |
| 1 | Physical |