TCP/IP Fundamentals
Learn IP addressing and subnetting, watch a real TCP three-way handshake with tcpdump, and understand the concrete tradeoffs between TCP and UDP by capturing both kinds of traffic yourself.
You'll see networking taught with two different layer models, and it's worth knowing both exist so neither confuses you later. The OSI model has seven layers (Physical, Data Link, Network, Transport, Session, Presentation, Application) and is mostly a teaching/reference framework. The TCP/IP model has four (Link, Internet, Transport, Application) and is what real protocol stacks actually implement. This project — and the rest of this roadmap — lives almost entirely in two layers: the Internet layer (IP: addressing and routing packets between networks) and the Transport layer (TCP and UDP: getting data reliably, or quickly, between two specific programs).
Everything else in this roadmap builds on this project directly: DNS runs over UDP (mostly) at this layer, HTTP runs over TCP (or QUIC, which itself runs over UDP), and load balancers make decisions at exactly the boundary between the transport layer (L4) and the application layer (L7) that this project establishes.
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