Networking
How data gets from one device to another: IP addresses and subnets, ports, NAT and DHCP, routing, TCP, UDP, QUIC and WebSockets.
Beginner
3 guidesOSI model: what each of the seven layers does
The seven OSI layers, what each one handles with real protocol examples, how the TCP/IP model maps to them, and why layer numbers help with troubleshooting.
IPv4 vs IPv6: how IP addresses work
IPv4 addresses are 32 bits and IPv6 addresses are 128 bits. How each is written, which ranges are private, why IPv4 ran out, and how dual stack works.
What is a network port? Port numbers explained
A port is a 16-bit number that tells a host which program should receive traffic. Port ranges, common ports such as 22, 53 and 443, and how firewalls use them.
Intermediate
5 guidesTCP vs UDP: differences and when to use each
TCP delivers a reliable, ordered byte stream after a handshake; UDP sends independent datagrams with no setup. How they differ and which protocols use each.
Subnetting and CIDR notation, with worked examples
How a CIDR prefix such as /24 splits an IP address into network and host bits, how many addresses it holds, and worked IPv4 and IPv6 subnet examples.
NAT and DHCP: how devices on your network get online
DHCP gives each device an address, gateway and DNS servers, and NAT shares one public IPv4 address among them. How both work and why NAT blocks inbound traffic.
Routing vs switching: how routers and switches differ
Switches forward frames by MAC address inside one network; routers forward packets between networks by IP address. How each decides, plus ARP, gateways and BGP.
WebSockets explained: the handshake, uses and limits
A WebSocket upgrades one HTTP request into a two-way message channel. How the handshake works, when to pick SSE or polling instead, and proxy and auth caveats.
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