How do i identify the type of problem in my network?

I just wanna know how to identify the network problem in case of emergency... i know that there is something known as layers of communication and accordingly the network performs logically and problems can be identified and solved keeping those layers in mind. can anyone help me with the layers please!

There are 7 layers of network communication known as OSI Layers [open system interconnection] [IEEE standards]

1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transpot Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

The layers represent the functionality of the layers.
All the best!

Here is an image for representation! Have a look.


http://gallery.techarena.in/data/513...ence_model.JPG