Networking Fundamentals - Vol 7 - OSI Lower Layers
As a network engineer, you’ll find that many of the network issues you deal with are solved at lower layers. That’s why this guide looks at the lower levels of the OSI and TCP/IP models, focusing on the physical layer and the data link layer. The more you understand about the basics such as cabling errors and MAC address issues, the faster and more accurately you'll be able to diagnose problems.