In the page at https://drewdevault.com/2016/12/06/A-broad-intro-to-networking.html
the two paragraphs starting “This layer also has ownership over MAC addresses, …”
should really by in the following 2: Data link layer. Layer 1 is about the physical
cables and connectors, electrical signal levels, etc. MAC addresses are part of
the message framing and live in layer 2.
Conversely, the bit in 2: Data link layer about Cat 5 cable, etc, should be in