6 lessons
Framing techniques and CRC, the real error-detection workhorse
How a receiver knows exactly where one frame ends and the next begins, and the polynomial division trick (CRC) that catches errors far better than a simple checksum.
Frames, switches, and how a local network delivers mail
How raw bits get organized into frames, and why a switch is smarter than just a shared wire.
Sharing the wire without everyone talking at once
What happens when two devices try to send at the exact same instant, and the simple rules (CSMA/CD and CSMA/CA) that stop it from becoming chaos.
ALOHA and token passing: two more ways to share the channel
The classic Medium Access Control numericals — pure ALOHA, slotted ALOHA, and token passing — worked through step by step with the actual efficiency formulas.
ARP, or how a device finds its neighbor's fingerprint
The knock-on-every-door trick your computer uses to translate an IP address into a MAC address before it can send anything.
Bridges, and how Ethernet segments get joined without chaos
How a bridge grows a network beyond one shared segment, and the spanning tree trick that stops bridges from looping a frame forever.