Network troubleshooting

Network problems look alike from the application and are entirely different underneath. "Timeout" could be DNS, routing, a firewall, TLS, or the server being busy, and each has a different fix.

Work up the stack in order. Every layer depends on the ones below it, so testing HTTP before confirming DNS resolves means interpreting a failure that could come from anywhere.

1. Read the error precisely — it names the layer

The distinctions here do most of the diagnostic work, and they are routinely conflated: