Subject
Networking
How bytes move on the wire. Start with the journey of one packet across the internet, then the protocols one by one: TCP, UDP, QUIC, HTTP, FTP and ICMP. Written so that a connection, a window or a retransmission is something you can picture, not a slogan.
Articles
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The journey of a packet: how two machines talk across the internet
Follow one request from a laptop to a server on the other side of the world and back: the name lookup, the five envelopes, the first hop, NAT, the routers in between, and the bill in round trips.
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TCP: the reliable byte stream
What TCP actually guarantees, how a connection starts and ends, and the two windows that keep it from drowning the other side or the path.
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UDP: fire and forget, on purpose
What a datagram is, why some protocols choose no guarantees at all, what the sender has to do itself, the MTU trap, NAT and firewalls, and where UDP shows up.
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QUIC: the transport hiding inside UDP
Why a new transport was needed, how QUIC folds the TCP and TLS handshakes into one, streams that do not block each other, packet numbers, connection migration, HTTP/3, and what it costs.
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HTTP: what a request really carries
The request and response as text, methods and status codes, the headers that matter, how connections evolved from one request at a time to HTTP/3, caching, cookies, and HTTPS.
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FTP: the protocol with two connections
How FTP splits commands and data across two TCP connections, why active mode breaks behind NAT and passive mode fixes it, a session on the wire, the ASCII trap, why plain FTP is fading, and where it still lives.
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ICMP: how the network talks back
The messages routers and hosts send about packets: what ping and traceroute really do, port unreachable, fragmentation needed and the path MTU black hole, ICMPv6, and why blocking ICMP breaks things.