TCP/IP, HTTP, DNS, TLS, and how requests actually travel.
Handshakes, reliability machinery, and why QUIC exists.
Methods, status codes, HTTP/1.1 → 2 → 3, and what TLS actually does.
The resolution chain, record types, caching/TTLs, and DNS as a traffic-engineering tool.
The canonical interview walkthrough — from keystroke to rendered page, with the depth knobs.
The layer models that organize every networking answer — what each layer does and where real devices and bugs live.
CIDR without tears, private ranges, how NAT actually rewrites packets, and why IPv6 exists.
What a socket really is, the server accept loop, TIME_WAIT, and the errors every backend engineer must decode.