OSI Model

Last Thursday in class we did group presentations about the OSI model.  I left the class realizing how little I know about what exactly makes the internet work.  Adjacent layers in each of seven layers of the model seem really similar.  I thought it would be nice to find a website with a description that gave examples of what could go wrong if there was a glitch in each of the layers.  I was unable to find one, but here are my thoughts.

It seems obvious that if something does not run in the lowest layer, the physical, the internet would not function.  

If the data link layer fails to break data into bits or control the flow of data it seems as though there could be a data overload or slowed transmission.  I'm not sure if this is true.

But suppose an error occurs at the network layer, does that mean that the information would be directed to the wrong IP address/ computer?  

If there is a glitch on the transport level it seemed as though the data would be transferred, but not completely.  

The session layer is still a bit confusing to me, I imagine it has something to do with logging in our out to begin or end a session or maybe initiating communication via email or a messenger service.  Maybe a session layer would result in an inability to log in to something.  

I also wondered at which point an error might display on the computer screen in a browser window.  It seems that that would occur at the presentation layer.  For example when a photo is not formatted correctly it displays as an empty icon on the page.

It seems as though the application layer will only run if every other layer is working.  This seems problematic, because it would be difficult to diagnose the cause of a problem since it could be a result of an error or damage at any of the other 6 layers.

If there is anyone that can give some insight about errors that may occur at each level, that would be of interest to me in order to better understand the OSI model.