- Some will say it has 4 layers, some say 5
- in tcp/ip, the first 3 layers of OSI are combined to be the application layer.
→ application, presentation, session → application
- some books will say internet layer instead of netowrk layer
- data link and physcial layers are combined to the network access layer
- usually we use the 4 layer model
- 5 layer model:
→ data link and physical are separate

Index