1-A 2-A 3-A 4-A | 5 network 6 data 7 = Physical, Data Link, Network, Transport, Session, Presentation, Application 8 = App = 5-7, Transport = 4, Internet = 3, Network Access = 1-2 9 = Bits, frames, packets, segments | 10 = Standardization, interoperability, easier troubleshooting