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).

1. In the OSI model, data flows down the transmit layers, over the physical link, and then up through the receive layers.

And, Ethernet works at layer 4. But there is a relationship between security protocols and locations layer. The closer it gets to the physical layer, the better the security will be. The most ...