You know your packet's destination IP. The kernel knows the next hop's IP. But Ethernet frames are addressed to MAC addresses, not IPs. The protocol that bridges 'I want to talk to 192.168.1.1' and 'send an Ethernet frame to aa:bb:cc:dd:ee:ff' is ARP, and it's been silently making your local network work for 40 years. Knowing it explains a class of weird connectivity problems.
Engineering Craft
TypeScript, CI/CD, databases, observability -- the skills that make code production-ready.
