Internet from the Bottom Up
Trace one connection from raw packets up through addressing, transport, encryption, and the web — the minimum mental model of how the internet works.
- Reading time
- ~32 min (+35 min optional)
- Level mix
- 6 beginner · 8 intermediate
The internet looks like one network, but it’s a stack of independent protocols that each solve one job. This path walks up that stack: from individual packets bouncing through routers, to addressing, to the unreliable and reliable transport layers, to names and encryption, finishing at HTTP — the protocol that delivers most of what you read on the web.
By the end you should be able to explain, in one minute, what happens between pressing Enter on https://wikipedia.org and seeing the page.
Roadmap
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How data moves
A small, self-describing chunk of data that travels across a network. The internet's fundamental unit of communication.
Addressing
A numeric identifier for a network interface — how computers find each other on the internet.
- RouterOptional
A device that forwards IP packets between networks, deciding which neighbour gets each packet on its way to the destination.
- NATOptional
Network Address Translation — how a router lets many devices on a private network share one public IP address by rewriting addresses and ports on traffic passing through it.
- GatewayOptional
A network node that bridges two different networks — most commonly the "default gateway," the router that forwards traffic from your local network out to the rest of the internet.
Naming
The phone book of the internet — translates human-readable names like example.com into IP addresses.
Transport
A connectionless, "fire and forget" transport protocol. Faster than TCP but with no delivery, ordering, or reliability guarantees.
A reliable, ordered, stream-based transport protocol on top of IP. The plumbing under most internet traffic.
- SocketOptional
The OS abstraction that lets a program send and receive data over a network — the fundamental API sitting between application code and the TCP/IP stack.
Security
The protocol that encrypts and authenticates almost all secure traffic on the internet — the "S" in HTTPS, IMAPS, SMTPS, and many more.
- FirewallOptional
A barrier that filters network traffic against a set of rules, allowing or blocking packets by address, port, or protocol to protect a network or host.
Application
The request/response protocol that powers the web — how browsers and servers talk to each other.
- WebSocketOptional
A protocol that upgrades an HTTP connection into a full-duplex, persistent channel for sending messages back and forth in real time.
The big picture
- OSI ModelOptional
A seven-layer conceptual model for how networking protocols stack on top of each other — physical wires at the bottom, applications at the top.