Course
Networking for Engineers Who Touch Real Systems
The mental model of production networking: TCP/IP, DNS, TLS handshakes, NAT and proxies, and how to prove where a connection died with ss, tcpdump, and curl.
How a Connection Really Works
TCP vs UDP, ports and the five-tuple, and the TCP lifecycle — what 'reliable' buys you and why connections die slowly.
- 01TCP vs UDP: What 'Reliable' Actually Buys YouSequence numbers, ACKs, and datagrams: what TCP guarantees, what it doesn't, and why UDP drops are silent.20mOpen
- 02Ports, Sockets, and the Five-TupleHow the kernel demultiplexes connections, why bind() fails, and the listening address that quietly exposes you.20mOpen
- 03The TCP Lifecycle: Handshakes, Windows, and Slow DeathsSYN to RST: flow control vs congestion control, Nagle vs delayed ACKs, and why dead peers look alive for hours.25mMembers
Names, Trust, and the Boxes in the Middle
DNS resolution end-to-end, the TLS 1.3 handshake, and how NAT, proxies, and load balancers change who's actually talking.
- 01DNS Resolution: From Stub Resolver to Authoritative AnswerTrace a query from getaddrinfo to the authoritative server, and learn the caching and search-domain failure modes.25mMembers
- 02The TLS Handshake: Certificates, Key Exchange, and SNIWhat TLS 1.3 negotiates in one round trip, how cert validation really works, and the verify=False bug that ships.25mMembers
- 03NAT, Proxies, and Load Balancers: Who's Actually TalkingConntrack, SNAT, L4 vs L7 proxies, PROXY protocol, and why trusting X-Forwarded-For is an auth bypass.20mMembers
Reading the Wire in Production
The diagnostic toolkit: ss for socket state, tcpdump for ground truth, and curl to bisect failures by layer.
- 01ss and /proc/net: What Your Host Thinks Is ConnectedRead the kernel's socket table: listeners, CLOSE-WAIT leaks, SYN-SENT stalls, and auditing for things you didn't deploy.20mPremium
- 02tcpdump: Capturing the Truth When the Logs LieBPF filters, flags on the wire, the capture-both-ends method, and what TLS does and doesn't hide from a sniffer.30mPremium
- 03curl as a Diagnostic Instrument and the Failures That MatterBisect DNS, TCP, TLS, and HTTP with -v and -w, pin requests to one backend, and catalog the failure modes.25mPremium