The summary.
THE THREE THINGS EVERY CONNECTION NEEDS
A physical or wireless link, an address, and an agreed protocol.
Almost every networking problem is one of those three.
DIAGNOSE FROM THE BOTTOM UPWARD
Link, then address, then routing, then name resolution, then the service itself.
A problem at a lower layer makes everything above it fail. Most problems are lower than people assume.
BANDWIDTH IS NOT THE ONLY MEASUREMENT
Latency and packet loss frequently matter more. A fast connection to a distant server still feels slow.
Small packet loss can halve effective throughput.
TEST ON A CABLE
It separates a wireless problem from a connection problem, and most "slow internet" is wireless.
ON EXTENDERS
They typically halve throughput. A wired access point does not.
An extender placed where the signal is already weak rebroadcasts a weak signal.
THE CHEAPEST DIAGNOSTIC THERE IS
Swap the cable.
WHAT SERVERS DO DIFFERENTLY FROM CLIENTS
They listen. Anything listening and reachable from the internet is found by scanning within hours.
