Where Do the 7 layers “fit”?
Or, where is Presentation 6
the dividing line ?
between hdw & Session 5
Data /Link 2 ?
Implementing the Model
User Space Software
Some More Definitions
• User Space Software - Code that executes as any
program that a normal user could compile and run
• OS Space Software - Code that executes on the
host CPU but in a mode or with special access that
normal users can not use
• „Firmware‟ - Code that executes on a processor
(special or general purpose) that is different from the
host CPU; may be in PROM or RAM downloaded from
• Hardware - Generally special purpose VLSI and
analog/linear interface components
Assigning the 7 layers