04 Try it yourself Interactive

Which layer owns this problem?

“Which layer does this happen at” is the single most common OSI interview question, and it is almost never answered well, because guessing a plausible layer and knowing the right one look identical until the follow-up arrives. This console runs the drill properly. Pick a symptom, and each press of Next moves one step: state the fault, rule out one tempting layer by naming something it does not have, rule out a second, and only then name the owner. Nothing plays on its own. Next, Back and Reset, or the arrow keys.

Problem 1 of 5
a receiver that cannot keep up
Rose marks a layer that has been ruled out, with the reason in the narration. Green marks the layer that owns the problem. A layer with no mark has not been considered yet, and the stat row names the layer under test on each step.
Press Next to begin. Each press moves the diagnosis one step.


      

        
Problem1 / 5

        
Layer under test–

        
Owner–

        
Ruled out0

      


      

      

        
        
        
        step 0 / 0