Short essays on how the internet works under the hood — networking concepts explained simply, the meaning behind IP and DNS data, and practical ways to use these tools.
The console names CORS as the thing that stopped you, when CORS is the mechanism that would have let you through. What makes a request plain enough to skip the preflight, why posting JSON never is, which wildcards credentials take away, and why none of it constrains a script running outside a browser.
Read →The first digit carries almost all of the meaning, and the specific numbers settle arguments you would otherwise guess at. Why four different redirect codes exist, what separates 401 from 403 and 404 from 410, and which machine a 502 blames that a 504 does not.
Read →Bandwidth, connection state, and application work each give way in a different manner, and which one goes first decides who can fix it. Why a half-open TCP connection costs the server real memory, how a 15-byte request turns into 750 kB aimed at somebody else, and what a log full of source addresses is actually worth.
Read →One runs on a port of its own, the other hides inside ordinary web traffic, and underneath they encrypt exactly the same thing. The ports and RFCs behind each, what your network can still see either way, and which one fits where.
Read →Two fields decide where every message to your domain goes. Why the lowest preference number wins, what happens when a domain publishes no MX at all, why an MX must never point at a CNAME, and how to declare that you accept no mail.
Read →Every device in your house has its own address, and the internet only ever sees one of them. What your router rewrites in each packet, why mappings expire on two very different clocks, how anything gets in from outside, and what carrier-grade NAT takes away.
Read →Nearly sixty port numbers in one table, with the transport each service actually runs on and the name IANA has registered for it, plus why the registry says nCube License Manager where you expect Oracle, and which numbers deserve a second look on a public host.
Read →Two protocols carry almost everything on the internet: one checks that every packet arrives, the other never looks back. How TCP guarantees delivery, why UDP trades that safety for speed, their headers side by side, and how to tell which one a service is using.
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