Learning path
Networking from the ground up
Follow a web request from the bottom up, from how a device gets an address and its packets cross NAT and the routes of the internet, to DNS names, reliable TCP connections, TLS encryption, HTTP and the newer QUIC and WebSockets.
Step 1 of 10 · 20 min read
How IP addresses work
What an IP address identifies, how IPv4 and IPv6 addresses are written and divided into networks, which ranges are reserved, and how a packet travels from one address to another.
Step 2 of 10 · 12 min read
How a device joins a network
What happens in the first seconds after a device connects to a network, from getting an IPv4 address with DHCP and finding neighbors with ARP to configuring IPv6 with router advertisements, SLAAC, Neighbor Discovery and DHCPv6.
Step 3 of 10 · 13 min read
How NAT works
How network address translation lets many devices share one public IPv4 address, how NATs map and filter traffic, and how STUN, TURN and ICE still connect two devices that are both behind one.
Step 4 of 10 · 11 min read
How internet routing works
How the independent networks of the internet find paths to each other with the Border Gateway Protocol, from autonomous systems and AS paths to route selection, business relationships, route hijacks and leaks, and RPKI.
Step 5 of 10 · 15 min read
How DNS works
How the Domain Name System turns names like www.example.com into IP addresses, from the tree of domain names and the servers that hold them to caching, record types, message formats and security.
Step 6 of 10 · 17 min read
How TCP works
How the Transmission Control Protocol turns unreliable packets into a reliable stream of bytes, from ports and the three-way handshake to acknowledgments, retransmission, flow control and congestion control.
Step 7 of 10 · 15 min read
How TLS works
How Transport Layer Security protects data on the internet, from the cryptographic building blocks and the TLS 1.3 handshake to certificates, the key schedule, resumption and what TLS cannot hide.
Step 8 of 10 · 16 min read
How HTTP works
How the Hypertext Transfer Protocol carries the web, from URLs, requests, methods and status codes to caching, cookies and the three versions in use today, HTTP/1.1, HTTP/2 and HTTP/3.
Step 9 of 10 · 12 min read
How QUIC works
How QUIC, the transport protocol under HTTP/3, combines the jobs of TCP and TLS on top of UDP, from its packets, connection IDs and streams to its one-round-trip handshake, loss recovery and connection migration.
Step 10 of 10 · 13 min read
How WebSockets work
How WebSockets give a web page a lasting two-way connection to a server, from the HTTP upgrade that opens it to frames, masking, pings and the closing handshake, and how they run over HTTP/2 and HTTP/3.