The Physical Layer includes cable specs, pin-out patterns, voltages, hubs, repeaters, network cards, protocol standards (RJ45, V series modem standards) and even host bus adapters (HBA).

A tutorial on the Open Systems Interconnection (OSI) networking reference model plus tips on how to memorize the seven layers.

The third layer of the OSI Model, the network layer, is where most network engineers focus their time and expertise. As Darragh commented in my post on the data link layer, Layer 2 is cool but ...

Also called a "layer 1 switch," "crosspoint switch," "crossbar switch" and "NxN switch." See physical layer and OSI model. THIS DEFINITION IS FOR PERSONAL USE ONLY.