12 parts · 21 chapters

Computer Networking, Complete

Every distributed system, API and web page rides on a stack of protocols designed decades apart. Knowing what each layer guarantees, and what it does not, explains latency, timeouts, outages and security problems that look mysterious from the application.

Twelve parts: layers, honestly; Ethernet and switching; IP and routing including BGP; TCP in depth; congestion control; UDP and QUIC; DNS; TLS; HTTP from 1.1 to 3; NAT and firewalls; capture and analysis with tcpdump and Wireshark; and a capstone that implements a small TCP stack over a TUN device.

Start reading · Part 0 Present as slides
layers · Ethernet and switching · IP and routing · TCP in depth · congestion control · UDP and QUIC · DNS · TLS · HTTP/1.1 to 3 · NAT and firewalls · tcpdump and Wireshark · a TCP stack over TUNeveryone without a CS degree · backend, infra and SRE engineers
layersWhat each layer adds, and the leaky reality of the OSI model.
IP and routingAddresses, subnets, routing tables, BGP and how the internet is glued together.
TCPHandshakes, sequence numbers, windows, retransmission, congestion control.
modern transportUDP, QUIC and HTTP/3.
naming and securityDNS resolution, caching and attacks; TLS 1.3 handshakes and certificates.
practicetcpdump, Wireshark, and a TCP stack you build.
00

Layers, Honestly

Layers and encapsulation · The end-to-end argument
2 ch · ~12 min01

Ethernet and Switching

Frames, ARP and switches
1 ch · ~8 min02

IP and Routing

Addresses, subnets and routes · Anycast and path MTU
2 ch · ~12 min03

TCP in Depth

Handshake, bytes and close · Retransmission, Nagle and keep-alive
2 ch · ~12 min04

Congestion Control

Windows that grow and shrink · Bufferbloat and application design
2 ch · ~12 min05

UDP and QUIC

Transport rebuilt · Operating QUIC
2 ch · ~12 min06

DNS

Resolution and caching · Records, TTLs and failure modes
2 ch · ~12 min07

TLS

The handshake · Certificates in production
2 ch · ~12 min08

HTTP from 1.1 to 3

Three wires, one meaning · Where versions are terminated
2 ch · ~12 min09

NAT and Firewalls

NAT · Firewalls, security groups and egress
2 ch · ~12 min10

tcpdump and Wireshark

Capture and read
1 ch · ~8 min11

Capstone: A TCP Stack over a TUN Device

The build
1 ch · ~8 min
Built on Computers part 5How Computers Work part 5 introduced packets, TCP and sockets; this course goes the full depth. Distributed Systems, Cloud networking and Backend Debugging part 5 build on it.