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Sams Teach Yourself Network Troubleshooting in 24 Hours, Second Edition by Jonathan Feldman

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Layer Definitions

Although you definitely don’t want to get caught up in unnecessary details (avoiding that is the point here, after all), it is a good idea to discuss each layer so that you can correlate reality back to the model.

I have always agreed with my column-writing colleague; to someone who is not designing network software or hardware, the layers that really matter for troubleshooting purposes are: Physical (1), Data Link (2), Network (3), and Application (7). Read on, and you’ll see why.

Physical: Layer 1

The Physical layer includes everything from the power supply of a device to the way that electrons, photons, or radio waves that compose a network signal get from point A to point B, as well as everything that you can touch, from ...

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